Method for Controlling Uplink Power in a Wireless Communication System and Apparatus Therefor

ABSTRACT

A method for uplink (UL) power control of a User Equipment (UE) in a wireless communication system according to one embodiment of the present invention comprises receiving a Downlink (DL) Reference Signal (RS); measuring DL path-loss by using the DL RS; determining transmission power for an UL channel by using the measured path-loss; and transmitting the UL channel, wherein the DL RS used for determining the transmission power for the UL channel is determined based on configuration information indicated by a base station.

TECHNICAL FIELD

The present invention relates to a wireless communication system andmore particularly, a method for uplink power control and a device forthe method.

BACKGROUND ART

Mobile communication systems have been developed to provide voiceservices, while guaranteeing user activity. Service coverage of mobilecommunication systems, however, has extended even to data services, aswell as voice services, and currently, an explosive increase in traffichas resulted in shortage of resource and user demand for a high speedservices, requiring advanced mobile communication systems.

The requirements of the next-generation mobile communication system mayinclude supporting huge data traffic, a remarkable increase in thetransfer rate of each user, the accommodation of a significantlyincreased number of connection devices, very low end-to-end latency, andhigh energy efficiency. To this end, various techniques, such as smallcell enhancement, dual connectivity, massive Multiple Input MultipleOutput (MIMO), in-band full duplex, non-orthogonal multiple access(NOMA), supporting super-wide band, and device networking, have beenresearched.

DISCLOSURE Technical Problem

An object of the present invention is to provide a procedure for uplinkpower control which may be applied to a new wireless communicationsystem.

Also, since the new wireless communication system does not define acell-specific reference signal for pathloss estimation as in the LTEsystem, an object of the present invention is to provide a new downlinkreference signal for pathloss estimation.

Also, an object of the present invention is to provide an efficientmethod for a base station to configure/indicate a downlink referencesignal which is a basis for determining uplink channel transmissionpower.

Technical objects to be achieved by the present invention are notlimited to those described above. Other technical objects of the presentinvention may also be clearly understood from the descriptions givenbelow by those skilled in the art to which the present inventionbelongs.

Technical Solution

A method for uplink (UL) power control of a User Equipment (UE) in awireless communication system according to one embodiment of the presentinvention comprises receiving a Downlink (DL) Reference Signal (RS);measuring DL path-loss by using the DL RS; determining transmissionpower for an UL channel by using the measured path-loss; andtransmitting the UL channel, wherein the DL RS used for determining thetransmission power for the UL channel may be determined based onconfiguration information indicated by a base station.

Also, the UL channel may correspond to a Physical Uplink Control Channel(PUCCH) or a Physical Uplink Shared Channel (PUSCH).

Also, the DL RS may correspond to a Channel State Information (CSI)-RSand/or a Synchronization Signal/Sequence (SS) block.

Also, the configuration information may be indicated through RadioResource Control (RRC) signaling.

Also, the configuration information may include the number of the DL RSand/or index of the DL RS.

Also, when the DL RS is determined as a specific DL RS indicated throughthe configuration information, the specific DL RS may be updated throughMedium Access Control (MAC) Control Element (CE) signaling.

Also, when a plurality of candidate DL RSs are indicated through theconfiguration information, the DL RS may be determined as a specific DLRS indicated through Medium Access Control (MAC) Control Element (CE)signaling among the candidate DL RSs.

Also, when there exists a plurality of the UL channels to betransmitted, the DL RS may be determined independently for each ULchannel resource configuration mapped to each of the plurality of the ULchannels.

Also, when at least one candidate DS RS is indicated through theconfiguration information, the DL RS may be determined as a specificcandidate DL RS associated with each of the UL channel resourceconfigurations.

Also, each of the UL channel resource configurations may be mutuallyassociated with the at least one candidate DL RS based on an index ofeach of the UL channel resource configurations and an index of the atleast one candidate DL RS.

Also, the DL RS may be determined as a specific DL RS associated with aControl Resource SET (CORESET) set for the UE through the configurationinformation.

Also, when transmission of the UL channel is triggered by a DL channeltransmitted through the CORESET, the specific DL RS may correspond tothe CSI-RS and/or the SS block Quasi-co-Located (QCLed) with a DLchannel transmitted through the CORESET.

Also, when at least one candidate DL RS is indicated through theconfiguration information, the specific DL RS may be determined as theDL RS only when the specific DL RS is included in the at least onecandidate DL RS.

Also, when a beam change indication for the base station is received,the method for power control may further comprise increasingtransmission power of the determined UL channel as much as the amount ofpreconfigured power.

A User Equipment (UE) performing Uplink (UL) power control in a wirelesscommunication system according to another embodiment of the presentinvention comprises a Radio Frequency (RF) unit for transmitting andreceiving a radio signal; and a processor for controlling the RF unit,wherein the processor is configured to receive a Downlink (DL) ReferenceSignal (RS); measure DL path-loss by using the DL RS; determinetransmission power of a UL channel by using the measured path-loss; andtransmit the UL channel, wherein the DL RS used for determining thetransmission power for the UL channel may be determined based onconfiguration information indicated by a base station.

Advantageous Effects

According to one embodiment of the present invention, since an estimateof pathloss due to a downlink reference signal is used for determiningtransmission power of an uplink channel, transmission efficiency of anuplink channel is improved.

Also, according to one embodiment of the present invention, since adownlink reference signal used for determining transmission power of anuplink channel is configured/indicated by a base station, ambiguityabout which downlink reference signal is to be used by a UE is removed.

The advantageous effect that may be achieved from the present inventionare not limited to those described above, and it should be clearlyunderstood by those skilled in the art to which the present inventionbelongs that other effects not mentioned in this document may beachieved from the descriptions given below.

DESCRIPTION OF DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this application, illustrate embodiment(s) of the invention andtogether with the description serve to explain the principle of theinvention.

FIG. 1 shows the structure of a radio frame in a wireless communicationsystem to which an embodiment of the present invention may be applied.

FIG. 2 is a diagram illustrating a resource grid for one downlink slotin a wireless communication system to which an embodiment of the presentinvention may be applied.

FIG. 3 shows the structure of a downlink subframe in a wirelesscommunication system to which an embodiment of the present invention maybe applied.

FIG. 4 shows the structure of an uplink subframe in a wirelesscommunication system to which an embodiment of the present invention maybe applied.

FIG. 5 illustrates a self-contained subframe structure to which thepresent invention may be applied.

FIG. 6 exemplifies a sub-array partition model, which is a first TXRUvirtualization model option.

FIG. 7 exemplifies a full-connection model, which is a second TXRUvirtualization model option.

FIG. 8 illustrates a service area for each TXRU.

FIG. 9 is a flow diagram illustrating a method for UL power control of aUE according to one embodiment of the present invention.

FIG. 10 is a block diagram of a wireless communication device accordingto one embodiment of the present invention.

MODE FOR INVENTION

Some embodiments of the present invention are described in detail withreference to the accompanying drawings. A detailed description to bedisclosed along with the accompanying drawings are intended to describesome exemplary embodiments of the present invention and are not intendedto describe a sole embodiment of the present invention. The followingdetailed description includes more details in order to provide fullunderstanding of the present invention. However, those skilled in theart will understand that the present invention may be implementedwithout such more details.

In some cases, in order to avoid that the concept of the presentinvention becomes vague, known structures and devices are omitted or maybe shown in a block diagram form based on the core functions of eachstructure and device.

In this specification, a base station (BS) (or eNB) has the meaning of aterminal node of a network over which the base station directlycommunicates with a device. In this document, a specific operation thatis described to be performed by a base station may be performed by anupper node of the base station according to circumstances. That is, itis evident that in a network including a plurality of network nodesincluding a base station, various operations performed for communicationwith a device may be performed by the base station or other networknodes other than the base station. The base station (BS) may besubstituted with another term, such as a fixed station, a Node B, an eNB(evolved-NodeB), a Base Transceiver System (BTS), an access point (AP),g-NodeB (gNB), New RAT (NR) or 5G-NodeB Remote radio head (RRH),transmission point(TP), reception point(RP), transmission/receptionpoint (TRP), relay. Furthermore, the device may be fixed or may havemobility and may be substituted with another term, such as UserEquipment (UE), a Mobile Station (MS), a User Terminal (UT), a MobileSubscriber Station (MSS), a Subscriber Station (SS), an Advanced MobileStation (AMS), a Wireless Terminal (WT), a Machine-Type Communication(MTC) device, a Machine-to-Machine (M2M) device, or a Device-to-Device(D2D) device.

Hereinafter, downlink (DL) means communication from an eNB to UE, anduplink (UL) means communication from UE to an eNB. In DL, a transmittermay be part of an eNB, and a receiver may be part of UE. In UL, atransmitter may be part of UE, and a receiver may be part of an eNB.

Specific terms used in the following description have been provided tohelp understanding of the present invention, and the use of suchspecific terms may be changed in various forms without departing fromthe technical sprit of the present invention.

The following technologies may be used in a variety of wirelesscommunication systems, such as Code Division Multiple Access (CDMA),Frequency Division Multiple Access (FDMA), Time Division Multiple Access(TDMA), Orthogonal Frequency Division Multiple Access (OFDMA), SingleCarrier Frequency Division Multiple Access (SC-FDMA), and Non-OrthogonalMultiple Access (NOMA). CDMA may be implemented using a radiotechnology, such as Universal Terrestrial Radio Access (UTRA) orCDMA2000. TDMA may be implemented using a radio technology, such asGlobal System for Mobile communications (GSM)/General Packet RadioService (GPRS)/Enhanced Data rates for GSM Evolution (EDGE). OFDMA maybe implemented using a radio technology, such as Institute of Electricaland Electronics Engineers (IEEE) 802.11 (Wi-Fi), IEEE 802.16 (WiMAX),IEEE 802.20, or Evolved UTRA (E-UTRA). UTRA is part of a UniversalMobile Telecommunications System (UMTS). 3rd Generation PartnershipProject (3GPP) Long Term Evolution (LTE) is part of an Evolved UMTS(E-UMTS) using evolved UMTS Terrestrial Radio Access (E-UTRA), and itadopts OFDMA in downlink and adopts SC-FDMA in uplink. LTE-Advanced(LTE-A) is the evolution of 3GPP LTE.

Embodiments of the present invention may be supported by the standarddocuments disclosed in at least one of IEEE 802, 3GPP, and 3GPP2, thatis, radio access systems. That is, steps or portions that belong to theembodiments of the present invention and that are not described in orderto clearly expose the technical spirit of the present invention may besupported by the documents. Furthermore, all terms disclosed in thisdocument may be described by the standard documents.

In order to more clarify a description, 3GPP LTE/LTE-A is chieflydescribed, but the technical characteristics of the present inventionare not limited thereto.

General System to which the Present Invention May be Applied

FIG. 1 shows the structure of a radio frame in a wireless communicationsystem to which an embodiment of the present invention may be applied.

3GPP LTE/LTE-A support a radio frame structure type 1 which may beapplicable to Frequency Division Duplex (FDD) and a radio framestructure which may be applicable to Time Division Duplex (TDD).

FIG. 1(a) illustrates the radio frame structure type 1. A radio frameconsists of 10 subframes. One subframe consists of 2 slots in a timedomain. The time taken to send one subframe is called a TransmissionTime Interval (TTI). For example, one subframe may have a length of 1ms, and one slot may have a length of 0.5 ms.

One slot includes a plurality of Orthogonal Frequency DivisionMultiplexing (OFDM) symbols in the time domain and includes a pluralityof Resource Blocks (RBs) in a frequency domain. In 3GPP LTE, OFDMsymbols are used to represent one symbol period because OFDMA is used indownlink. An OFDM symbol may be called one SC-FDMA symbol or symbolperiod. An RB is a resource allocation unit and includes a plurality ofcontiguous subcarriers in one slot.

FIG. 1(b) illustrates the frame structure type 2. The radio framestructure type 2 consists of 2 half frames. Each of the half framesconsists of 5 subframes, a Downlink Pilot Time Slot (DwPTS), a GuardPeriod (GP), and an Uplink Pilot Time Slot (UpPTS). One subframeconsists of 2 slots. The DwPTS is used for initial cell search,synchronization, or channel estimation in UE. The UpPTS is used forchannel estimation in an eNB and to perform uplink transmissionsynchronization with UE. The guard period is an interval in whichinterference generated in uplink due to the multi-path delay of adownlink signal between uplink and downlink is removed.

In the frame structure type 2 of a TDD system, an uplink-downlinkconfiguration is a rule indicating whether uplink and downlink areallocated (or reserved) to all subframes. Table 1 shows theuplink-downlink configuration.

TABLE 1 Uplink- Downlink- Downlink to-Uplink config- SwitchpointSubframe number uration periodicity 0 1 2 3 4 5 6 7 8 9 0 5 ms D S U U UD S U U U 1 5 ms D S U U D D S U U D 2 5 ms D S U D D D S U D D 3 10 msD S U U U D D D D D 4 10 ms D S U U D D D D D D 5 10 ms D S U D D D D DD D 6 5 ms D S U U U D S U U D

Referring to Table 1, in each subframe of the radio frame, “D” isindicative of a subframe for downlink transmission, “U” is indicative ofa subframe for uplink transmission, and “S” is indicative of a specialsubframe including three types of a DwPTS, GP, and UpPTS. Anuplink-downlink configuration may be classified into 7 types. Thepositions and/or number of downlink subframes, special subframes, anduplink subframe are different in each configuration.

A point of time at which a change is performed from downlink to uplinkor a point of time at which a change is performed from uplink todownlink is called a switching point. The periodicity of the switchingpoint means a cycle in which an uplink subframe and a downlink subframeare changed is identically repeated. Both 5 ms and 10 ms are supportedin the periodicity of a switching point. If the periodicity of aswitching point has a cycle of a 5 ms downlink-uplink switching point,the special subframe S is present in each half frame. If the periodicityof a switching point has a cycle of a 5 ms downlink-uplink switchingpoint, the special subframe S is present in the first half frame only.

In all the configurations, 0 and 5 subframes and a DwPTS are used foronly downlink transmission. An UpPTS and a subframe subsequent to asubframe are always used for uplink transmission.

Such uplink-downlink configurations may be known to both an eNB and UEas system information. An eNB may notify UE of a change of theuplink-downlink allocation state of a radio frame by transmitting onlythe index of uplink-downlink configuration information to the UEwhenever the uplink-downlink configuration information is changed.Furthermore, configuration information is kind of downlink controlinformation and may be transmitted through a Physical Downlink ControlChannel (PDCCH) like other scheduling information. Configurationinformation may be transmitted to all UEs within a cell through abroadcast channel as broadcasting information.

Table 2 below shows a configuration (length of DwPTS/GP/UpPTS) of aspecial subframe.

TABLE 2 Normal cyclic prefix in downlink Extended cyclic prefix indownlink UpPTS UpPTS Special Normal Extended Normal Extended subframecyclic prefix cyclic prefix cyclic prefix cyclic prefix configurationDwPTS in uplink in uplink DwPTS in uplink in uplink 0  6592 · T_(s) 2192· T_(s) 2560 · T_(s)  7680 · T_(s) 2192 · T_(s) 2560 · T_(s) 1 19760 ·T_(s) 20480 · T_(s) 2 21952 · T_(s) 23040 · T_(s) 3 24144 · T_(s) 25600· T_(s) 4 26336 · T_(s)  7680 · T_(s) 4384 · T_(s) 5120 · T_(s) 5  6592· T_(s) 4384 · T_(s) 5120 · T_(s) 20480 · T_(s) 6 19760 · T_(s) 23040 ·T_(s) 7 21952 · T_(s) — — — 8 24144 · T_(s) — — —

The structure of a radio frame is only one example. The number ofsubcarriers included in a radio frame or the number of slots included ina subframe and the number of OFDM symbols included in a slot may bechanged in various ways.

FIG. 2 is a diagram illustrating a resource grid for one downlink slotin a wireless communication system to which an embodiment of the presentinvention may be applied.

Referring to FIG. 2, one downlink slot includes a plurality of OFDMsymbols in a time domain. It is described herein that one downlink slotincludes 7 OFDMA symbols and one resource block includes 12 subcarriersfor exemplary purposes only, and the present invention is not limitedthereto.

Each element on the resource grid is referred to as a resource element,and one resource block (RB) includes 12×7 resource elements. The numberof RBs NDL included in a downlink slot depends on a downlinktransmission bandwidth.

The structure of an uplink slot may be the same as that of a downlinkslot.

FIG. 3 shows the structure of a downlink subframe in a wirelesscommunication system to which an embodiment of the present invention maybe applied.

Referring to FIG. 3, a maximum of three OFDM symbols located in a frontportion of a first slot of a subframe correspond to a control region inwhich control channels are allocated, and the remaining OFDM symbolscorrespond to a data region in which a physical downlink shared channel(PDSCH) is allocated. Downlink control channels used in 3GPP LTEinclude, for example, a physical control format indicator channel(PCFICH), a physical downlink control channel (PDCCH), and a physicalhybrid-ARQ indicator channel (PHICH).

A PCFICH is transmitted in the first OFDM symbol of a subframe andcarries information about the number of OFDM symbols (i.e., the size ofa control region) which is used to transmit control channels within thesubframe. A PHICH is a response channel for uplink and carries anacknowledgement (ACK)/not-acknowledgement (NACK) signal for a HybridAutomatic Repeat Request (HARQ). Control information transmitted in aPDCCH is called Downlink Control Information (DCI). DCI includes uplinkresource allocation information, downlink resource allocationinformation, or an uplink transmission (Tx) power control command for aspecific UE group.

A PDCCH may carry information about the resource allocation andtransport format of a downlink shared channel (DL-SCH) (this is alsocalled an “downlink grant”), resource allocation information about anuplink shared channel (UL-SCH) (this is also called a “uplink grant”),paging information on a PCH, system information on a DL-SCH, theresource allocation of a higher layer control message, such as a randomaccess response transmitted on a PDSCH, a set of transmission powercontrol commands for individual UE within specific UE group, and theactivation of a Voice over Internet Protocol (VoIP), etc. A plurality ofPDCCHs may be transmitted within the control region, and UE may monitora plurality of PDCCHs. A PDCCH is transmitted on a single ControlChannel Element (CCE) or an aggregation of some contiguous CCEs. A CCEis a logical allocation unit that is used to provide a PDCCH with acoding rate according to the state of a radio channel. A CCE correspondsto a plurality of resource element groups. The format of a PDCCH and thenumber of available bits of a PDCCH are determined by an associationrelationship between the number of CCEs and a coding rate provided byCCEs.

An eNB determines the format of a PDCCH based on DCI to be transmittedto UE and attaches a Cyclic Redundancy Check (CRC) to controlinformation. A unique identifier (a Radio Network Temporary Identifier(RNTI)) is masked to the CRC depending on the owner or use of a PDCCH.If the PDCCH is a PDCCH for specific UE, an identifier unique to the UE,for example, a Cell-RNTI (C-RNTI) may be masked to the CRC. If the PDCCHis a PDCCH for a paging message, a paging indication identifier, forexample, a Paging-RNTI (P-RNTI) may be masked to the CRC. If the PDCCHis a PDCCH for system information, more specifically, a SystemInformation Block (SIB), a system information identifier, for example, aSystem Information-RNTI (SI-RNTI) may be masked to the CRC. A RandomAccess-RNTI (RA-RNTI) may be masked to the CRC in order to indicate arandom access response which is a response to the transmission of arandom access preamble by UE.

FIG. 4 shows the structure of an uplink subframe in a wirelesscommunication system to which an embodiment of the present invention maybe applied.

Referring to FIG. 4, the uplink subframe may be divided into a controlregion and a data region in a frequency domain. A physical uplinkcontrol channel (PUCCH) carrying uplink control information is allocatedto the control region. A physical uplink shared channel (PUSCH) carryinguser data is allocated to the data region. In order to maintain singlecarrier characteristic, one UE does not send a PUCCH and a PUSCH at thesame time.

A Resource Block (RB) pair is allocated to a PUCCH for one UE within asubframe. RBs belonging to an RB pair occupy different subcarriers ineach of 2 slots. This is called that an RB pair allocated to a PUCCH isfrequency-hopped in a slot boundary.

As more communication devices require greater communication capacity, anecessity of mobile broadband communication which is more improved thanthe existing radio access technology (RAT) has been raised. In addition,the massive MTC (Machine Type Communications) that provides variousservices anytime and anywhere by connecting a plurality of devices andobjects is also one of important issues, which is considered in a nextgeneration communication. Moreover, it has been discussed a design of acommunication system in which a service and/or a UE sensitive toreliability and latency. As such, an introduction of a next generationRAT has been discussed currently, which considers enhanced mobilebroadband communication, massive MTC, Ultra-Reliable and Low LatencyCommunication (URLLC), and the like, and such a technology is referredto as ‘new RAT (NR)’.

Self-Contained Subframe Structure

FIG. 5 illustrates a self-contained subframe structure to which thepresent invention may be applied.

In TDD system, in order to minimize data transmission delay, theself-contained subframe structure as shown in FIG. 5 has been consideredin 5 Generation new RAT. The shaded area in FIG. 5 shows a downlinkcontrol region, and the dark area shows an uplink control region. Inaddition, the area not marked in FIG. 5 may be used for a downlink (DL)data transmission or an uplink (UL) data transmission. In thecharacteristics of such a structure, a DL transmission and a ULtransmission may be sequentially progressed in a subframe, a DL data maybe transmitted and a UL ACK/NACK may be received in a subframe.Consequently, a time required for retransmitting data is reduced when adata transmission error occurs, and owing to this, the delay till thelast data forwarding may be minimized.

As an example of the self-contained subframe structure which may beconfigured/setup in a system operating based on New RAT, the followingat least four subframe types may be considered. Hereinafter, thedurations existed in each of the subframe types are numerated in timesequence.

1) DL control duration+DL data duration+guard period (GP)+UL controlduration

2) DL control duration+DL data duration

3) DL data duration+GP+UL control duration+UL control duration

4) DL data duration+GP+UL control duration

In such a self-contained subframe structure, a time gap is required fora process that an eNB and a UE switch from a transmission mode to areception mode or a process that an eNB and a UE switch from a receptionmode to a transmission mode. For this, a part of OFDM symbols on thetiming switching from DL to UL may be setup as GP, and such a subframetype may be referred to as ‘self-contained SF’.

Analog Beamforminq

In Millimeter Wave (mmW) band, a wavelength becomes short and aninstallation of a plurality of antenna elements is available in the samearea. That is, the wavelength in 30 GHz band is 1 cm, and accordingly,an installation of total 100 antenna elements is available in2-dimensional arrangement shape with 0.5 lambda (wavelength) intervalsin 5 by 5 cm panel. Therefore, in mmW band, beamforming (BF) gain isincreased by using a plurality of antenna elements, and accordingly,coverage is increased or throughput becomes higher.

In this case, each antenna element has a Transceiver Unit (TXRU) suchthat it is available to adjust a transmission power and a phase, andindependent beamforming is available for each frequency resource.However, it has a problem that effectiveness is degraded in a costaspect when TXRUs are installed in all of about 100 antenna elements.Accordingly, a method has been considered to map a plurality of antennaelements in a single TXRU and to adjust a direction of beam by an analogphase shifter. Such an analog beamforming technique may make only onebeam direction throughout the entire band, and there is a disadvantagethat frequency selective beamforming is not available.

As a middle form between a Digital BF and an analog BF, B number ofhybrid BF may be considered which is smaller than Q number of antennaelement. In this case, directions of beams that may be transmittedsimultaneously are limited lower than B number; even it is changedaccording to a connection scheme between B number of TXRUs and Q numberof antenna elements.

FIGS. 6 and 7 illustrate a representative connection scheme between aTXRU and an antenna element. More particularly, FIG. 6 exemplifies asub-array partition model, which is a first TXRU virtualization modeloption and FIG. 7 exemplifies a full-connection model, which is a secondTXRU virtualization model option. In FIGS. 6 and 7, TXRU virtualizationmodel represents a relation between an output signal of a TXRU and anoutput signal of an antenna element.

As shown in FIG. 6, in the case of the virtualization model in which aTXRU is connected to a sub-array, an antenna element is connected toonly a single TXRU. Different from this, in the case of thevirtualization model in which a TXRU is connected to all antennaelements, an antenna element is connected to all TXRUs. In thesedrawings, W represents a phase vector which is multiplied by an analogphase shifter. That is, a direction of analog beamforming is determinedby W. Here, mapping between CSI-RS antenna ports and TXRUs may be 1 to 1(1:1) or 1 to many (1:N).

Reference Signal (RS)

In a wireless communication system, a signal may be distorted duringtransmission because data is transmitted through a radio channel. Inorder for a reception end to accurately receive a distorted signal, thedistortion of a received signal needs to be corrected using channelinformation. In order to detect channel information, a method ofdetecting channel information using the degree of the distortion of asignal transmission method and a signal known to both the transmissionside and the reception side when they are transmitted through a channelis mainly used. The aforementioned signal is called a pilot signal orreference signal (RS).

Furthermore recently, when most of mobile communication systems transmita packet, they use a method capable of improving transmission/receptiondata efficiency by adopting multiple transmission antennas and multiplereception antennas instead of using one transmission antenna and onereception antenna used so far. When data is transmitted and receivedusing multiple input/output antennas, a channel state between thetransmission antenna and the reception antenna should be detected inorder to accurately receive the signal. Accordingly, each transmissionantenna should have an individual reference signal.

In a mobile communication system, an RS may be basically divided intotwo types depending on its purpose. There are an RS having a purpose ofobtaining channel state information and an RS used for datademodulation. The former has a purpose of obtaining, by a UE, to obtainchannel state information in the downlink, and accordingly, acorresponding RS should be transmitted in a wideband, and a UE should becapable of receiving and measuring the RS although the UE does notreceive downlink data in a specific subframe. Furthermore, the former isalso used for radio resources management (RRM) measurement, such ashandover. The latter is an RS transmitted along with correspondingresources when an eNB transmits the downlink. A UE may perform channelestimation by receiving a corresponding RS and thus may demodulate data.The corresponding RS should be transmitted in a region in which data istransmitted.

A downlink RS includes one common RS (CRS) for the acquisition ofinformation about a channel state shared by all of UEs within a cell andmeasurement, such as handover, and a dedicated RS (DRS) used for datademodulation for only a specific UE. Information for demodulation andchannel measurement may be provided using such RSs. That is, the DRS isused only for data demodulation, and the CRS is used for the twopurposes of channel information acquisition and data demodulation.

The reception side (i.e., UE) measures a channel state based on a CRSand feedbacks an indicator related to channel quality, such as a channelquality indicator (CQI), a precoding matrix index (PMI) and/or a rankindicator (RI), back to the transmission side (i.e., an eNB). The CRS isalso called a cell-specific RS. On the other hand, a reference signalrelated to the feedback of channel state information (CSI) may bedefined as a CSI-RS.

In 3GPP LTE(-A) system, it is defined that a UE reports CSI to a BS.Here, the CSI is commonly called for the information that may representa quality of a radio channel (or also referred to as a link) establishedbetween a UE and an antenna port. For example, the CSI may correspond toa rank indicator (RI), a precoding matrix indicator (PMI), and/or achannel quality indicator (CQI), and the like. Here, RI represents rankinformation of a channel, and this may mean the number of streams that aUE receives through the same time-frequency resource. Since RI isdetermined with being dependent upon long-term fading of a channel, theRI is fed back from a UE to a BS with a period longer than CQI,generally. PMI is a value that reflects a channel space property, andrepresents a precoding index that a UE prefers based on a metric such asSINR. CQI is a value that represents signal strength, and means areception SINR that is obtainable when a BS uses the PMI, generally.

In 3GPP LTE(-A) system, a BS may setup a plurality of CSI processes to aUE, and may receive CSI report for each process. Here, the CSI processmay include CSI-RS for signal quality measurement from a BS andCSI-interference measurement (CSI-IM) resource for interferencemeasurement.

The DRS may be transmitted through resource elements if datademodulation on a PDSCH is required. A UE may receive information aboutwhether a DRS is present through a higher layer, and the DRS is validonly in the case that a corresponding PDSCH has been mapped. The DRS mayalso be called a UE-specific RS or Demodulation RS (DMRS).

FIG. 8 illustrates reference signal patterns mapped to downlink resourceblock pairs in a wireless communication system to which the presentinvention may be applied.

Referring to FIG. 8, a downlink resource block pair, a unit in which areference signal is mapped may be represented in the form of onesubframe in a time domain X 12 subcarriers in a frequency domain. Thatis, in a time axis (an x axis), one resource block pair has a length of14 OFDM symbols in the case of a normal cyclic prefix (CP) (in FIG.7(a)) and has a length of 12 OFDM symbols in the case of an extendedcyclic prefix (CP) (FIG. 7(b)). In the resource block lattice, resourceelements (REs) indicated by ‘0’, ‘1’, ‘2’, and ‘3’ mean the locations ofthe CRSs of antenna port indices ‘0’, ‘1’, ‘2’, and ‘3’, respectively,and REs indicated by ‘D’ mean the location of a DRS.

In the case that an eNB uses a single transmission antenna, referencesignals for a single antenna port are arrayed.

In the case that an eNB uses two transmission antennas, referencesignals for two transmission antenna ports are arrayed using a timedivision multiplexing (TDM) scheme and/or a frequency divisionmultiplexing (FDM) scheme. That is, different time resources and/ordifferent frequency resources are allocated in order to distinguishbetween reference signals for two antenna ports.

Furthermore, in the case that an eNB uses four transmission antennas,reference signals for four transmission antenna ports are arrayed usingthe TDM and/or FDM schemes. Channel information measured by thereception side (i.e., UE) of a downlink signal may be used to demodulatedata transmitted using a transmission scheme, such as singletransmission antenna transmission, transmission diversity, closed-loopspatial multiplexing, open-loop spatial multiplexing or a multi-userMIMO antenna.

In the case that a multi-input multi-output antenna is supported, when aRS is transmitted by a specific antenna port, the RS is transmitted inthe locations of resource elements specified depending on a pattern ofthe RS and is not transmitted in the locations of resource elementsspecified for other antenna ports. That is, RSs between differentantennas do not overlap.

In an LTE-A system, that is, an evolved and developed form of the LTEsystem, the design is necessary to support a maximum of eighttransmission antennas in the downlink of an eNB. Accordingly, RSs forthe maximum of eight transmission antennas must be also supported. Inthe LTE system, only downlink RSs for a maximum of four antenna portshas been defined. Accordingly, in the case that an eNB has four to amaximum of eight downlink transmission antennas in the LTE-A system, RSsfor these antenna ports must be additionally defined and designed.Regarding the RSs for the maximum of eight transmission antenna ports,both of the aforementioned RS for channel measurement and theaforementioned RS for data demodulation should be designed.

One of important factors considered in designing an LTE-A system isbackward compatibility, that is, that an LTE UE should operate properlyalso in the LTE-A system, which should be supported by the system. Froman RS transmission aspect, in the time-frequency domain in which a CRSdefined in LTE is transmitted in a full band every subframe, RSs for amaximum of eight transmission antenna ports should be additionallydefined. In the LTE-A system, if an RS pattern for a maximum of eighttransmission antennas is added in a full band every subframe using thesame method as the CRS of the existing LTE, RS overhead is excessivelyincreased.

Accordingly, the RS newly designed in the LTE-A system is basicallydivided into two types, which include an RS having a channel measurementpurpose for the selection of MCS or a PMI (channel state information-RS,channel state indication-RS (CSI-RS), etc.) and an RS for thedemodulation of data transmitted through eight transmission antennas(data demodulation-RS (DM-RS)).

The CSI-RS for the channel measurement purpose is characterized in thatit is designed for a purpose focused on channel measurement unlike theexisting CRS used for purposes of measurement, such as channelmeasurement and handover, and for data demodulation. Furthermore, theCSI-RS may also be used for a purpose of measurement, such as handover.The CSI-RS does not need to be transmitted every subframe unlike the CRSbecause it is transmitted for a purpose of obtaining information about achannel state. In order to reduce overhead of a CSI-RS, the CSI-RS isintermittently transmitted on the time axis.

In the LTE-A system, a maximum of eight transmission antennas aresupported in the downlink of an eNB. In the LTE-A system, in the casethat RSs for a maximum of eight transmission antennas are transmitted ina full band in every subframe using the same method as the CRS in theexisting LTE, RS overhead is excessively increased. Accordingly, in theLTE-A system, an RS has been separated into the CSI-RS of the CSImeasurement purpose of the selection of MCS or a PMI and the DM-RS fordata demodulation, and thus the two RSs have been added. The CSI-RS mayalso be used for a purpose, such as RRM measurement, but has beendesigned for a main purpose of the acquisition of CSI. The CSI-RS doesnot need to be transmitted every subframe because it is not used fordata demodulation. Accordingly, in order to reduce overhead of theCSI-RS, the CSI-RS is intermittently transmitted on the time axis. Thatis, the CSI-RS has a period corresponding to a multiple of the integerof one subframe and may be periodically transmitted or transmitted in aspecific transmission pattern. In this case, the period or pattern inwhich the CSI-RS is transmitted may be set by an eNB.

In order to measure a CSI-RS, a UE should be aware of information aboutthe transmission subframe index of the CSI-RS for each CSI-RS antennaport of a cell to which the UE belongs, the location of a CSI-RSresource element (RE) time-frequency within a transmission subframe, anda CSI-RS sequence.

In the LTE-A system, an eNB has to transmit a CSI-RS for each of amaximum of eight antenna ports. Resources used for the CSI-RStransmission of different antenna ports must be orthogonal. When one eNBtransmits CSI-RSs for different antenna ports, it may orthogonallyallocate the resources according to the FDM/TDM scheme by mapping theCSI-RSs for the respective antenna ports to different REs.Alternatively, the CSI-RSs for different antenna ports may betransmitted according to the CDM scheme for mapping the CSI-RSs topieces of code orthogonal to each other.

When an eNB notifies a UE belonging to the eNB of information on aCSI-RS, first, the eNB should notify the UE of information about atime-frequency in which a CSI-RS for each antenna port is mapped.Specifically, the information includes subframe numbers in which theCSI-RS is transmitted or a period in which the CSI-RS is transmitted, asubframe offset in which the CSI-RS is transmitted, an OFDM symbolnumber in which the CSI-RS RE of a specific antenna is transmitted,frequency spacing, and the offset or shift value of an RE in thefrequency axis.

A CSI-RS is transmitted through one, two, four or eight antenna ports.Antenna ports used in this case are p=15, p=15, 16, p=15, . . . , 18,and p=15, . . . , 22, respectively. A CSI-RS may be defined only for asubcarrier interval Δf=15 kHz.

RS Virtualization

In mmW band, a PDSCH transmission is available only to a single analogbeam direction on a time by analog beamforming. As a result, an eNB isable to transmit data only to a small number of UEs in a specificdirection. Accordingly, on occasion demands, analog beam direction isdifferently configured for each antenna port, and a data transmissionmay be performed to a plurality of UEs in several analog beam directionssimultaneously.

Hereinafter, four sub-arrays are formed by dividing 256 antenna elementsinto four equal parts, and an exemplary structure in which a TXRU isconnected to each sub-array shown in FIG. 8 is described mainly.

FIG. 8 is a diagram illustrating a service area for each TXRU.

When each sub-array includes total 64 (8×8) antenna elements in2-dimensional array shape, a region corresponding to a horizontal anglearea of 15 degrees and a vertical angle area of 15 degrees may becovered by specific analog beamforming. That is, a region in which aneNB is needed to serve is divided into a plurality of areas, and eacharea is served at a time. In the following description, it is assumedthat CSI-RS antenna port and TXRU are mapped in 1-to-1 manner.Accordingly, an antenna port and a TXRU may have the same meaning in thefollowing description.

As shown in an example of FIG. 8a , in the case that all TXRUs (antennaport, sub-array) have the same analog beamforming direction, thethroughput of the corresponding region may be increased by forming adigital beam having higher resolution. In addition, the throughput ofthe corresponding region may be increased by increasing rank oftransmission data to the corresponding region.

As shown in FIG. 8b , in the case that each TXRU (antenna port,sub-array) has different analog beamforming direction, a simultaneousdata transmission becomes available in a corresponding subframe (SF) toUEs distributed in wider area. For example, among four antenna ports,two of them are used for a PDSCH transmission to UE1 in area 1 and theremaining two of them are used for a PDSCH transmission to UE2 in area2.

FIG. 8b shows an example that PDSCH 1 transmitted to UE1 and PDSCH 2transmitted to UE2 are Spatial Division Multiplexed (SDM). Differentfrom this, FIG. 8c shows an example that PDSCH 1 transmitted to UE1 andPDSCH 2 transmitted to UE2 may be transmitted by being FrequencyDivision Multiplexed (FDM).

Between the scheme of serving an area by using all antenna ports and thescheme of serving several areas simultaneously by dividing antennaports, in order to maximize cell throughput, a preferred scheme may bechanged depending on a RANK and an MCS served to a UE. In addition, apreferred scheme may also be changed depending on an amount of data tobe transmitted to each UE.

An eNB calculates cell throughput or scheduling metric that may beobtained when serving an area by using all antenna ports, and calculatescell throughput or scheduling metric that may be obtained when servingtwo areas by dividing antenna ports. The eNB compares the cellthroughput or the scheduling metric that may be obtained through eachscheme, and selects a final transmission scheme. Consequently, thenumber of antenna ports participated in a PDSCH transmission is changedfor each SF (SF-by-SF). In order for an eNB to calculate a transmissionMCS of a PDSCH according to the number of antenna ports and reflect itto scheduling algorithm, a CSI feedback from a UE proper to it may berequested.

Beam Reference Signal (BRS) and Beam Refinement Reference Signal (BRRS)

BRSs may be transmitted in at least one antenna port p={0, 1, . . . ,7}. BRS sequence r_(l)(m) may be defined as Equation 1 below.

$\begin{matrix}{{{r_{l}(m)} = {{\frac{1}{\sqrt{2}}\left( {1 - {2 \cdot {c\left( {2m} \right)}}} \right)} + {j\; \frac{1}{\sqrt{2}}\left( {1 - {2 \cdot {c\left( {{2\; m} + 1} \right)}}} \right)}}}, {m = 0},1,\ldots \mspace{11mu},{{8 \cdot \left( {N_{RB}^{{{ma}\; x},{DL}} - 18} \right)} - 1}} & \left\lbrack {{Equation}\mspace{14mu} 1} \right\rbrack\end{matrix}$

In Equation 1, l=0, 1, . . . , 13 may represents an OFDM symbol number.In addition, c(i) represents a pseudo-random sequence generator, and maybe initialized by Equation 2 on a starting point of each OFDM symbol.

$\begin{matrix}{{C_{init} = {{2^{10} \cdot \left( {{7 \cdot \left( {n_{s} + 1} \right)} + l^{\prime} + 1} \right) \cdot \left( {{2 \cdot N_{ID}^{cell}} + 1} \right)} + {2 \cdot N_{ID}^{cell}} + 1}},\mspace{20mu} {n_{s} = \left\lfloor \frac{l}{7} \right\rfloor},\mspace{20mu} {l^{\prime} = {l\; {mod}\; 7}}} & \left\lbrack {{Equation}\mspace{14mu} 2} \right\rbrack\end{matrix}$

BRRS may be transmitted in maximum eight antenna ports p=600, . . . ,607. A transmission and a reception of BRRS may be dynamically scheduledin a downlink resource allocation in xPDCCH.

BRRS sequence r_(l,n) _(s) (m) may be defined as Equation 3 below.

$\begin{matrix}{{{r_{l,n_{s}}(m)} = {{\frac{1}{\sqrt{2}}\left( {1 - {2{c\left( {2m} \right)}}} \right)} + {j\; \frac{1}{\sqrt{2}}\left( {1 - {2{c\left( {{2m} + 1} \right)}}} \right)}}},{m = 0},1,\ldots \mspace{11mu},{\left\lfloor {\frac{3}{8}N_{RB}^{{{ma}\; x},{DL}}} \right\rfloor - 1}} & \left\lbrack {{Equation}\mspace{14mu} 3} \right\rbrack\end{matrix}$

In Equation 3, ns represents a slot number in a radio frame, lrepresents an OFDM symbol number in the slot, and c(n) represents apseudo-random sequence. The pseudo-random sequence generator may beinitialized by Equation 4 on a starting point of each OFDM symbol.

c _(init)=2¹⁰(7( n _(s)+1)+l+1)(2N _(ID) ^(BRRS)+1)+2N _(ID) ^(BRRS)+1

n _(s) =n _(s) mod 20  [Equation 4]

In Equation 4, N_(ID) ^(BRRS) may be set to a UE through RRC (RadioResource Control) signaling.

BRS may be transmitted to each subframe and may be transmitted in adifferent analog beam direction for each port. BRS may be used by an eNBto determine an approximate analog beam direction to a UE. If anapproximate analog beam direction toward a UE is determined based on theBRS, the eNB may refine the analog beam direction toward the UE moreaccurately by transmitting BRRS in more precise/finer directions withina given analog beam direction range.

As described above, the term for a reference signal used for determiningan analog beam direction toward a UE is not limited to theaforementioned BRS or BRRS and may be replaced with/referred to asvarious other reference signals which may be used for performing thesame function. For example, BRS may be replaced with/referred to asprimary/first CSI-RS, Primary synchronization signal/sequence (PSS),Secondary synchronization signal/sequence (SSS), SynchronizationSignal/Sequence (SS) block, NR-PSS, and/or NR-SSS; and BRRS may bereplaced with/referred to as secondary/second CSI-RS.

PSS, SSS and/or PBCH may be transmitted within an ‘SS block (SSB)’. AnSS block does not exclude other signal. One or more SS block(s) maycomprise an ‘SS burst’. One or more SS burst(s) may comprise an ‘SSburst set’. The number of SS bursts within an SS burst set may befinite.

DL Phase Noise Compensation Reference Signal (DL PCRS)

A PCRS associated with xPDSCH may be transmitted in antenna port P=60 orP=61 as it is signaled in a DCI format. The PCRS is existed only in thecase that xPDSCH transmission is associated with a corresponding antennaport, and the PCRS in this case may be a valid reference for phase noisecompensation. The PCRS may be transmitted only in physical resourceblocks and symbols to which corresponding xPDSCH is mapped. The PCRS maybe the same in all symbols that correspond to xPDSCH allocation.

For both of the antenna ports P=60, 61, PCRS sequence r(m) may bedefined as Equation 5 below.

$\begin{matrix}{{{r(m)} = {{\frac{1}{\sqrt{2}}\left( {1 - {2 \cdot {c\left( {2m} \right)}}} \right)} + {j\; \frac{1}{\sqrt{2}}\left( {1 - {2 \cdot {c\left( {{2m} + 1} \right)}}} \right)}}},\mspace{85mu} {m = 0},1,\ldots \mspace{11mu},{\left\lfloor {N_{RB}^{{{ma}\; x},{DL}}/4} \right\rfloor - 1}} & \left\lbrack {{Equation}\mspace{14mu} 5} \right\rbrack\end{matrix}$

In Equation 5, c(i) represents pseudo-random sequence. The pseudo-randomsequence generator may be initialized by Equation 6 on a starting pointof each subframe.

c _(init)=(└n _(s)/2┘+1)·(2_(ID) ^((n) ^(SCID) ⁾+1)·2¹⁶ +n_(SCID)  [Equation 6]

In Equation 6, n_(ID) ^((i)) may be determined as below when i=0, 1.

-   -   In the case that a value for n_(ID) ^(PCRS,i) is not provided by        a higher layer, n_(ID) ^((i))=N_(ID) ^(cell)    -   Otherwise, n_(ID) ^((i))=n_(ID) ^(PCRS,i)

A value of n_SCID may be set to 0, unless it is particularly determined.In xPDSCH transmission, n_SCID may be provided by a DCI formationassociated with xPDSCH transmission.

Beam Management Framework

The following DL Layer 1 (L1)/Layer 2 (L2) beam management proceduresmay be supported within one or more TRPs:

-   -   P-1 (procedure): P-1 may be used for enabling measurement of        different TRP Tx beams by a UE to support selection of TRP        transmission (Tx) beams/UE reception (Rx) beam(s). A typical        case of TRP beamforming may include intra/inter-TRP Tx beam        sweeping from a set of different beams (or which uses a set        comprising different beams). A typical case of UE beamforming        may include UE Rx beam sweeping from a set of different beams        (or which uses a set of different beams). TRP Tx beams and UE Rx        beams may be determined jointly or sequentially. When the beams        are determined sequentially, for example, a TRP Tx beam is first        determined, and a UE Tx beam may then be determined based on the        determined TRP Tx beam.    -   P-2 (procedure): P-2 is used for enabling measurement of        different TRP Tx beams by a UE to determine/change        inter/intra-TRP Tx beam(s). In other words, since P-2 is        intended to be used by a UE to determine optimal/relevant TRP Tx        beam(s), different TRP Tx beams are measured (more specifically,        an RS transmitted through different TRP Tx beams is measured),        and repeated measurement of the same TRP Tx beam is not        performed. Therefore, when P-2 is configured, a Tx beam to which        an RS (for example, CSI-RS) resource is transmitted/mapped        within the same/one RS resource set may differ for each        resource. At this time, Rx beam used for measurement of        different TRP Tx beam(s) may be set to the same beam, which may        correspond to the Rx beam determined/selected by P-3 described        below.

The P-2 may be configured for a UE through RRC signaling. For example,P-2 may be configured/indicated for a UE as ‘ResourceRep (orCSI-RS-ResourceRep) RRC parameter’ is configured/indicated as ‘off’. Atthis time, the ‘ResourceRep RRC parameter’ may correspond to an RRCparameter which indicates whether ‘repetition is on/off’. If the‘ResourceRep RRC parameter’ indicates ‘repetition on’ (namely theparameter is configured as on), the UE may assume that an eNB maintainsa fixed Tx beam for each RS resource within the same RS set while if‘repetition off’ is indicated (namely the parameter is configured asoff), the UE may assume that the eNB does not maintain a fixed Tx beamfor each RS resource within the same RS set. At this time, theResourceRep RRC parameter when the RS is a CSI-RS may be referred to as‘CSI-RS-ResourceRep RRC parameter’. The CSI-RS-ResourceRep parameterassociated with a CSI-RS resource set defines whether a repetition inconjunction with spatial domain transmission filter is ON/OFF (inparticular, whether spatial domain transmission filter is the same) atgNB-side.

If the UE is configured with the higher-layer parameterCSI-RS-ResourceRep set to ‘OFF’ (namely if P-2 is configured), the UEmay not assume that the CSI-RS resources within the resource set aretransmitted with the same downlink spatial domain transmission filterand with the same number of ports in every symbol.

The P-2 may perform UE measurement on a smaller Tx beam set than P-1(namely a smaller set of beams) for more precise beam refinement thanP-1. Therefore, P-2 may be regarded as a special case of P-1.

-   -   P-3 (procedure): When a UE uses beamforming, P-3 is used for        enabling (repeated) measurement of the same TRP Tx beam by the        UE to determine/change a UE Rx beam. In other words, since P-3        is intended to be used by a UE to determine an optimal/relevant        Rx beam, the same TRP ‘Tx’ beam may be measured/received        ‘repeatedly’ by using a different ‘Rx’ beam (more specifically,        an RS transmitted through the same TRP Tx beams may be measured        by using a different Rx beam). At this time, the same TRP ‘Tx’        beam measured repeatedly may be a Tx beam determined/selected        beforehand through the P-2 procedure. Therefore, when P-3 is        configured, a Tx beam to which RS (for example, CSI-RS)        resources are transmitted/mapped within the same RS resource set        may be the same for each resource.

The P-3 may be configured for a UE through RRC signaling. For example,the P-3 may be configured/indicated for a UE as ‘ResourceRep (orCSI-RS-ResourceRep) RRC parameter’ is configured/indicated as ‘on’.

If the UE is configured with the higher-layer parameterCSI-RS-ResourceRep set to ‘ON’, the UE may assume that the CSI-RSresources within the resource set are transmitted through the samedownlink spatial domain transmission filter, where the CSI-RS resourceswithin the resource set are transmitted in different OFDM symbols. Also,the UE is not expected to receive different periodicity for all of theCSI-RS resources within the set.

To achieve simultaneous change of the TRP Tx beam and UE Rx beam, theP-2 and P-3 procedures may be performed jointly (or sequentially) and/ormultiple times. The P-3 procedure may or may not have a physical layerprocedure. Also, the P-3 may support management of multiple Tx/Rx beampairs for a UE.

The aforementioned procedures may be applied over the whole frequencyband and may be used for a single/multiple beams for each TRP.

In what follows, an UL beam management procedure will be described.

An UL beam management procedure may be defined similarly to the DL beammanagement procedure above and may be largely divided into the followingtypes:

-   -   U-1 (procedure): U-1 may be used for enabling TRP measurement of        different UE Tx beams to support selection of the UE Tx beam/TRP        Rx beam. The U-1 procedure may correspond to the P-1 procedure        described above.    -   U-2 (procedure): U-2 may be used for enabling TRP measurement of        different TRP Rx beams to change/select inter/intra-TRP Rx        beam(s). The U-2 procedure may correspond to the P-2 procedure        described above.    -   U-3 (procedure): When a UE uses beamforming, U-3 may be used for        enabling (repetitive) TRP measurement of the same TRP Rx beam to        change UE Tx beams. The U-3 may correspond to the P-3 procedure        described above.

With regard to these procedures, an indication of various Tx/Rx beammatching/correspondence-related information may be supported.

UL beam management may be performed based on the following channel/RS.

-   -   Physical Random Access Channel (PRACH)    -   Sounding Reference Signal (SRS)    -   DM-RS

A TRP and a UE may have Tx/Rx beam correspondence/matching. Or the TRPmay not have Tx/Rx beam correspondence/matching and/or the UE may nothave Tx/Rx beam correspondence/matching.

A CSI-RS may support DL Tx beam sweeping and UE Rx beam sweeping. Atthis time, the CSI-RS may be used for the P-1, P-2, and P-3 procedures.

An NR CSI-RS may support the following mapping structure:

-   -   Np CSI-RS port(s) may be mapped to each (sub) time unit. The        same CSI-RS antenna ports may be mapped across (sub) time units.        Here, the “time unit” refers to OFDM symbols where n≥1 in a        configured/reference numerology. The OFDM symbols comprising a        time unit may be consecutive or inconsecutive in the time        domain. Methods for port multiplexing may include FDM, TDM, CDM,        or various combinations thereof.    -   Each time unit may be partitioned into sub-time units.        Partitioning methods may include, for example, TDM, Interleaved        FDMA (IFDMA), and an OFDM symbol-level partitioning method,        where the OFDM symbol has an OFDM symbol length the same as or        shorter (namely larger subcarrier spacing) than the reference        OFDM symbol length (subcarrier spacing); and other methods in        addition thereto are also included.    -   The mapping structure may be used for supporting multiple        panels/Tx chains.    -   The following CSI-RS mapping options may be available for Tx and        Rx beam sweeping:

1. Option 1: The Tx beam(s) are the same across sub-time units withineach time unit. The Tx beam(s) are different across time units.

2. Option 2: The Tx beam(s) are different across sub-time units withineach time unit. The Tx beam(s) are the same across time units.

3. Option 3 (a combination of Option 1 and Option 2): within one timeunit, Tx beam(s) are the same across sub-time units. Tx beam(s) withinanother time unit are different across sub-time units. In terms of thenumber and period, different time units may be combined together.

Only one of Tx sweeping and Rx sweeping may be available. The mappingstructure above may be configured by a composition of one or more CSI-RSresources.

UL Pathloss Control (PC) in the New RAT (NR)

In designing UL PC, the following factors need to be considered.

-   -   There is no cell-specific reference signal for estimation of        pathloss as in the LTE system.    -   Beam-based transmission/reception    -   Analog beamforming in the eNB/UE    -   Multi-beam/multi-stream transmission    -   Multi-numerology    -   Inter-TRP information exchange    -   Dynamic TDD

As a starting point of UL PC, a design as shown below may be taken intoaccount:

-   -   Fractional power control of the LTE as a framework    -   DL RS for pathloss measurement (for example, an RS in the DL        beam management P-1, P-2, and P-3 based on a multiple or single        beam scenario)    -   Separate PC settings for UL control and data channel

Furthermore, UL PC may be designed from the following aspects:

-   -   Numerology-specific parameter setting    -   Separate PC settings for multi-beam/multi-stream UL

In the case of NR-PUSCH which targets at least enhanced mobile broadband(eMBB):

-   -   Open-loop power control based on pathloss estimate may be        supported. Pathloss may be estimated by using a DL RS for        measurement and/or fractional power control may be supported. At        this time, which DL RS(s) (at this time, beamforming may be        applied to the RS) are used for measurement may be indicated        implicitly/explicitly by an eNB, which will be described in        detail below.    -   And/or closed loop power control based on network (NW) signaling        may be supported. At this time, dynamic UL-power adjustment may        be taken into account.

Furthermore, numerology-specific power control (for example,numerology-specific power control parameters), beam-specific powercontrol parameters, power control for other RSs and physical channels,power control with respect to the grant without involving PUSCH ifsupported, and/or power control for each layer (group) may be taken intoaccount for UL PC.

New functions such as OFDM-based UL transmission and single symbol ULcontrol channel are considered for adoption in the design of the NRsystem. In what follows, based on what has been described above, an ULpower control procedure in the NR will be described, which includesbasic components such as pathloss compensation, power offset, transmitpower control (TPC) command, and some add-on functions.

1. Basic Parameters for UL Power Control

1-1. Pathloss Compensation

According to UL power control in the current LTE system, two types ofpathloss compensation are considered. One is full pathloss compensation,and the other is fractional pathloss compensation. In the NR system,after a UE measures reference signal received power (RSRP) by using aspecific RS type, pathloss between the UE and its associated gNB may bederived by using the (upper-layer filtered) RSRP.

The UL transmission power from the UE may be fully or partiallycompensated by taking into account estimated pathloss. First, fullpathloss compensation may maximize fairness among cell-edge UEs. Inother words, power received from the cell-edge UE by the gNB side may becomparable to the power received from a cell-center UE. On the otherhand, if fractional pathloss compensation is used, the power receivedfrom a cell-center UE by the gNB side may be much higher than the powerreceived from the cell-edge UE. While the pathloss of the cell-edge UEmay be compensated by adjusting other power parameters or offsets sothat the power received from the cell-edge UE may be controlledproperly, the power received from the cell-center UE already provides asufficient amount of power for most cases, and therefore may beredundant.

In the case of UL data channel transmission, such redundant/extra powermay be used to improve spectral efficiency by applying a higher MCSlevel (for example, the cell-center UE may use a smaller number of PRBsfor the same TB size). On the other hand, in the case of UL controlchannel transmission which uses a fixed amount of resources, sinceuplink control information (UCI) (payload) size does not depend on theUE position or channel state, it is unclear whether spectral efficiencyis improved by using the redundant/extra power. Therefore, it ispreferable to consider full compensation for power control of the ULcontrol channel.

Also, in the case of fractional pathloss compensation for UL datachannel transmission, a received power difference between thecell-center UE and the cell-edge UE may be adjusted by using the valueof a fractional pathloss compensation factor, and this value may bevaried according to the cell radius and target performance.

Considering the descriptions above as a whole, as a result, it ispreferable to consider full pathloss compensation for power control ofthe UL control channel.

1-2. Power Offset Due to Data Rate

In general, to support a higher data rate, it is expected that moretransmission power is needed. However, it is inefficient for powercontrol of an UL data channel to use the fractional pathlosscompensation and power offset (namely Delta_TF setting in the LTE)simultaneously depending on the data rate. Moreover, in the current LTE,this type of power offset is not supported for the rank higher than 2.Therefore, in the NR, it is necessary to consider supporting onlyfractional pathloss compensation without a power offset settingdepending on data rate.

As a result, for power control of an UL data channel in the NR, it isnecessary to consider supporting only fractional pathloss compensationwithout a power offset setting depending on data rate.

1-3. TPC Command

To compensate channel variations due to fast fading, TPC command may beused. While PUCCH power may be adjusted by TPC command signaled by DLassignment DCI in the current LTE, PUSCH (or SRS) power may be adjustedby TPC command signaled by UL grant DCI. Moreover, for UL transmissionwithout involving associated DCI such as semi-persistent scheduling(SPS), periodic CSI, or SRS, the TPC command may be signaled to aspecific UE group by using the DCI format 3/3A.

Two types of TPC procedures may be employed for updating UL transmissionpower; one is accumulative TPC, and the other is absolute TPC.Accumulative TPC relies on TPC values of relatively small step size andis well-suited for fine-tuning of UE transmission power. On the otherhand, absolute TPC may be useful for boosting UE transmission power atonce by using TPC values of relatively large step size.

As described above, by taking into account cell deployment, UL physicalchannel type (for example, control or data), and wireless channelcondition, various methods may be proposed for the design of an UL powercontrol procedure for NR from the aspect of pathloss compensation, poweroffset, and TPC command.

2. Additional Features for Power Control in the NR

2-1. Beamforming Operation

In the NR design, particularly in the high-frequency band (for example,above 6 GHz), it is necessary to consider introduction of analog (orhybrid) beamforming-based operation. With this analog beamforming, gNBTx/Rx beam sweeping (for example, TDM among different gNB Tx/Rx beams)may be required not only for transmission of a DL common signal,synchronization signal (for example, PSS/SSS of the LTE) and/orbroadcast system information (for example, physical broadcast channel(PBCH) of the LTE) but also for transmission of DL/UL control and datachannels for servicing UEs located in different areas (or at differentbeam directions). In this case, it may be necessary to considerdifferentiation of power control parameters among different beams for aUE since power required for UL performance would be different from beamto beam for a UE.

As a result, since power required for UL performance would be differentfrom beam to beam for a UE, differentiation of power control parametersamong different beams for the UE may need to be taken intoconsideration.

However, in the case of accumulative TPC procedure, a further study isneeded to determine whether PC parameter separation for each beam isbetter than a common accumulative TPC procedure regardless of beamchange or switching. Taking into account the fact that the alreadystabilized transmit power levels are desired to remain as much aspossible unless beam change occurs at different TRPs, the latterindicates that the accumulative TPC procedure is not reset even if aserving beam is changed by a beam management procedure. Since there mayexist a configurable additional power offset to be applied to the TPCaccumulation process whenever beam change or switching occurs within thesame TRP for each targeted service requiring higher reliability such asURLLC and enhanced Vehicle-to-everything (eV2X), potential power controlmismatch due to beam change/switching may be relieved. Also, this may beapplied for retransmission for improving performance of HARQ which needsto be performed according to a proper higher-layer configurationprovided by the gNB.

As a result, in the case of accumulative TPC procedure, according to atarget service requiring high reliability (for example, URLLC and eV2X),it may be needed to take into account a configurable additional poweroffset which may be applied to a common TPC accumulation processwhenever beam change or switching occurs within the same TRP.

To examine further in detail what are proposed by the present inventionrelated to the descriptions above, the following issue related to the“beam specific power control parameters” needs to be considered amongthe specifics related to the UL PC:

-   -   How to perform transmit power control (TPC) of a transmit signal        when, while a reception point (eNB) targeted by a transmission        signal (when a UE performs UL transmission) is fixed, the Rx        beam of the corresponding reception point is changed (by        specific beam management) (and/or when the Tx beam of the        corresponding transmission point (namely UE) is changed).

As one method to solve the aforementioned issue, TPCchain/procedure/parameter(s) are made to be configured independently foreach specific beam so that power control may be applied/performedindependently for each beam. This is so because whentransmission/reception beam direction is changed, the optimal transmitpower level may be changed for reasons such as changing of a receptioninterference environment.

However, independent configuration for each beam does not alwaysguarantee optimal operation. This is so because since the receptionpoint itself remains the same, but only Tx/Rx beams for the sametransmission/reception point are changed, maintaining previous(stabilized) PC such as TPC accumulation as much as possible may be moreadvantageous in terms of performance. However, since optimal powercontrol due to beam change/switching may be changed slightly, at leastone method among those proposed below may be applied to improvereliability:

-   -   As described above, the TPC procedure due to beam        change/switching is not allowed to be initialized for the same        TRP. An example of a condition for determining TRPs as the same        one may include “a case where beam change/switching occurs based        on a CSI-RS configured in the form of a (sub-) time unit”. More        specifically, when the corresponding CSI-RS is configured as        being intended for specific beam management or configured as a        single CSI-RS resource and/or a plurality of CSI-RS resources        but having the same TRP characteristics such that a specific        group is configured for the plurality of CSI-RS resources,        recognition of TRPs as the same one may be performed implicitly        or explicitly (in other words, an indication which indicates        whether they are the same TRP may be performed implicitly or        explicitly). At this time, Quasi-co-Location (QCL) signaling may        be used as an explicit indicator for recognizing the same TRP.    -   (In addition to the description above) when beam        change/switching occurs within the same TRP as described above,        a specific power offset value (P_offset_beam) to be added to the        power control procedure (as a one-time value) may be configured        by RRC configuration (and/or L2-level configuration such as        Medium Access Control (MAC) Control Element (CE) and/or L1-level        configuration such as DCI). In other words, in the case of TPC        accumulation, if beam change/switching occurs, the UE may add        P_offset_beam to the current power value (for the purpose of        reliability). The P_offset_beam value may be configured by RRC        configuration (and/or L2-level configuration such as MAC CE        and/or L1-level configuration such as DCI)        differently/independently for a specific service (for example,        V2X, URLLC, and eMBB) or for each L1 parameter (for example,        RNTI) corresponding to each service.

In the expression “beam change/switching” of the embodiment above, beamchange and beam switching may connote operations distinguished from eachother. For example, beam change may refer to the case where change of aserving beam occurs (namely a configured serving beam is changed toanother beam) when only one serving beam is configured while beamswitching may refer to the case where, when a plurality of serving beamsare configured, dynamic beam switching occurs among configured servingbeams (for example, (semi-) open-loop (OL) transmission based on beamcycling defined/configured by a specific (time-domain) pattern).

In the case of beam change, how a beam change command is delivered to aUE has to be considered first. More specifically, if a beam changecommand is delivered via an L1 signal (for example, DCI) or an L2 signal(for example, MAC CE), a power offset value having a large range/highresolution may be delivered within the corresponding signal/message.Also, a beam switching command may be delivered via an L1 signal (forexample, DCI) or an L2 signal (for example, MAC CE), a (separate)specific power offset value(s) may be delivered within the correspondingsignal/message. At this time, information about when to apply thecorresponding power offset value(s) may also be indicated implicitly orexplicitly. For example, when information related to a switching periodfor beam switching/cycling is configured together (with a beam switchingcommand and/or a power offset value(s)) or configured separately, a UEmay be configured to apply the corresponding power offset value(s) eachtime beam switching occurs according to the information related to theswitching period (for example, when a pattern where beam switching isperformed after transmission of the same beam two times is configuredfor a UE, the UE applies an indicated/corresponding power offset valueonly to the beam transmitted first after beam switching but does notapply the power offset value to the second transmitted beam).

And/or an indicator about whether to inherit or reset a previous TPCaccumulation value may also be delivered together when an eNB delivers abeam change command (and/or beam switching command) to a UE. At thistime, the indicator may be delivered by being included in an L1 and/orL2 command message which delivers a beam change command (and/or beamswitching command).

If it is indicated to inherit, the TPC value (for example, +X dB, 0 dB,or −Y dB, . . . ) indicated by a specific closed-loop TPC field(transmitted together) may be accumulated to the TPC accumulation valueinherited by the UE. Furthermore, the UE may apply/add the P_offset_beamvalue additionally to the inherited TPC accumulation value (as aone-time operation or whenever beam switching is performed in the caseof beam switching).

If reset is indicated, the UE may apply the TPC value (for example, +XdB, 0 dB, or −Y dB, . . . ) indicated by a specific closed-loop TPCfield (transmitted together) as an initial TPC accumulation value of thenewly initialized (reset) PC procedure. For example, after calculatingan open-loop pathloss control (OLPC) component, the UE may apply theindicated TPC value to the calculated OLPC component as a new, initialTPC accumulation value (in other words, accumulates the indicated TPCvalue to the OLPC component). Furthermore, the UE may apply/add theP_offset_beam value additionally to the OLPC component (as a one-timeoperation or each time beam switching is performed in the case of beamswitching).

Also, SRS transmission may be essential for closed-loop PC, where arelationship between SRS transmission time and beam change/switchingcommand delivery time needs to be specified clearly.

For example, when a UE performs beam change (or switching) from beam 1to beam 2, it is customary to transmit an SRS in the beam 2 directionafter beam change is performed, but by defining/configuring an operationof the UE to transmit the SRS in the beam 2 direction before beamchange, more precise PC may be performed. To this end, at the time ofaperiodic SRS triggering (for example, via an L1 message), in which beamto transmit the SRS may be indicated explicitly. Similarly, an operationof the UE may be defined/configured in such a way to performtransmission of a plurality of SRSs simultaneously at one time, theplurality of SRSs belonging to a predefined, specific “SRS beam set”pre-configured (separately). For example, when candidate beams which maybe a target of SRS transmission are defined/configured by using beam 1to beam 4, a UE configuration may be conducted so that the “SRS beamset” may include all of the four beams or only part of the beams (forexample, {beam 2, beam 3}). The configuration may be re-configured by L3(for example, by RRC), L2 (for example, by MAC) and/or L1 (for example,by DCI) signaling afterwards.

In this way, if a specific “SRC beam set” is configured, and an SRStriggering message is received, the UE may operate so that SRStransmission using/through beams belonging to the SRS beam set isperformed on the SRS resource(s) indicated by a triggering message (orpreconfigured in conjunction with each beam) (in the latter case, SRStransmission with respect to the beam 2 and SRS transmission withrespect to the beam 3 are performed in conjunction with the respectiveSRS resource(s)).

In addition, if the same TRP Rx beam is retained, but only the UE Txbeam has to be changed due to beam blockage, a kind of fallback modepower control method may be defined/configured. For example, whileseparate/independent power control parameter(s) for the second best beam(pair) are determined/configured/stored during the UL beam sweepingprocedure, the UE may be configured to initiate UL transmission based onspecific fallback mode power control (for example, SRS transmission,PUCCH transmission and/or PUSCH transmission). More specifically, giventhat a first best Tx beam and/or Rx beam (pair), second best Tx beamand/or Rx beam (pair), and so on in a specific direction are determinedby UL beam management, and this information is provided from a UE to aneNB or vice versa, when the UE first performs specific UL transmission(for example, SRS transmission, PUCCH transmission and/or PUSCHtransmission), beamforming transmission/reception which takes intoaccount the first best Tx beam and/or Rx beam (pair) may be initiated.At this time, an operation may be defined/configured so that whenretransmission is attempted due to the reason that demodulation of thetransmission signal at the receiver (for example, eNB) fails (forexample, the receiver sends NACK as feedback), the transmitter (forexample, UE) is made to perform the fallback mode power control and/orretransmission based on other beam (pair). In particular, in a system towhich “synchronous HARQ” is applied, where the system isdefined/configured so that retransmission is initiated according to ascheduled timeline while an explicit scheduling grant for retransmissionis not provided separately, a specific Tx beam and/or Rx beam (pair)and/or specific power control parameter(s) (which include aP_offset_beam value (for each retransmission)) to be applied for then-th retransmission (for n=1, 2, . . . ) may bedefined/configured/provided to the UE beforehand in the form of aspecific pattern, and the UE may initiate UL transmission/retransmissionbased on the specific Tx beam and/or Rx beam (pair) and/or specificpower control parameter(s).

At this time, a different transmission method may be used depending onwhether an UL transmission target of the UE is PUCCH or PUSCH. Forexample, in the case of PUCCH, an associated configuration forusing/applying power control parameter(s) (including a relatedP_offset_beam value (for each retransmission)) (as a fallback) for thecase where a second best UE Tx beam is used with respect to the TRP Rxbeam set for the first best (UL) beam pair by the eNB may be provided,and the UE may initiate transmission/retransmission based on theprovided associated configuration. In the case of PUSCH, an associatedconfiguration for using/applying power control parameter(s) (including arelated P_offset_beam value (for each retransmission)) for the secondbest (UL) beam pair may be provided, and the UE may initiatetransmission/retransmission based on the provided associatedconfiguration.

A specific k-th optimal Tx and/or Rx beam (pair) applied whentransmission in the form of the fallback described above is performed(for example, specific n-th retransmission) may be configured to have arelatively wider beam width. In particular, this configuration may beconfigured/applied to be used as a fallback (for example, for thepurpose of dealing with an error occurrence with respect to the firstoptimal beam (pair)). And/or at the time of fallback transmission (forexample, n-th retransmission), the UE operation may beconfigured/restricted in advance so that the aforementioned “beamswitching” transmission is initiated.

2-2. Power Transient Period

In general, it is expected that the amount of information conveyed viaan UL data channel would be much larger than that conveyed via ULcontrol channel. Therefore, the required power for UL data channeltransmission may also be larger than needed for transmission of the ULcontrol channel. For NR design, TDM may be considered as a multiplexingstructure between UL data and control channels for latency reduction,flexible UL/DL configuration, and analog beamforming. If UL data andcontrol channels are multiplexed according to the TDM scheme, it may benecessary to handle power imbalance between the two different channelsrelatively larger compared to the current LTE system. Moreover, takinginto account various OFDM numerology (for example, different subcarrierspacing or symbol duration) used for NR, it may be necessary to handle apower transient period between UL data and control channels for aspecific numerology (for example, large subcarrier spacing).

As a result, it is necessary to consider an additional feature for ULpower control in the NR such as an analog beamforming operation and apower transient period.

2-3 Per-TRP and Per-Power Control for Each TRP and Layer

Coordinated transmission schemes across multiple intra/inter-TRPs may bediscussed. In particular, for high frequency bands in NR, the number ofdominant rays per TRP or single panel may be limited, which, forexample, is observed up to rank 2 for most cases. Therefore, in order toachieve high Single User (SU)-MIMO spectral efficiency, coordinatedtransmission schemes across multiple TRPs need to be thoroughlyinvestigated in NR, including Coordinated multi-point (CoMP) dynamicpoint selection (DPS) and independent-layer joint transmission (JT).When DL-related DCI indicates the transmission rank and an appliedcoordinated scheme, the DCI decoding latency at the UE side may be onemajor problem whenever analog beamforming is applied at a given timeinstance. This is so because the DCI transmission may be performed by aserving TRP, but actual data transmission may be performed by anotherTRP.

In the case of independent-layer JT where particular layer(s) may betransmitted from different TRPs, the corresponding UL transmission powerper layer-group may need to be configured and controlled by gNB, sinceat least pathloss from different TRPs may be different. Also, a separateUL power control procedure targeting a different TRP may bedefined/configured from the aspect of UL-CoMP context.

As a result, UL power control per TRP and per layer-group needs to bedefined/configured for properly supporting DPS and independent-layer JTin NR.

In what follows, a method for beam-specific power control for UL will bedescribed.

In the case of beam-specific power control, NR defines beam specificopen- and closed-loop parameters. Furthermore, NR defines beam commonparameters. Details on “beam specific” may be defined, especiallyregarding handling layer/layer-group/panel specific/beam groupspecific/beam pair link specific power control.

If the UE may be configured for two waveforms, gNB may recognize thepower headroom differences for the different waveforms. Regarding theaforementioned fact, a configuration/specific/report offset may bedefined, and details of power control parameters such as P_c, max orother open-/closed-loop parameters.

Codebook based transmission for UL may be supported at least by thefollowing signaling in UL grant:

-   -   SRS resource indicator (SRI)+Transmit PMI (TPMI)+Transmit Rank        Indicator (TRI),

where TPMI may be used to indicate preferred precoder over SRS ports ofSRS resources selected/indicated by the SRI. When a single SRS source isconfigured, SRI may not exist/may not be signaled. In this case, TPMImay be used to indicate preferred precoder over the SRS ports of aconfigured single SRS resource.

Furthermore, an indication about selection of a plurality of SRSresources may be supported.

For N closed-loop power control procedures, namely, f_(c)(i,l) for NRPUSCH power control for a serving cell (c), the following operatingassumption may be configured/defined:

-   -   N is up to 2.

In the case of accumulative TPC command mode, the closed-loop powercontrol process (f(i)) may be reset by RRC reconfiguration of P₀ and α.

Power Headroom (PH) calculation for PUSCH transmission may be supported,where, for example, the PH may be calculated by Equation 7 below.

PH _(c) =P _(cmax,c)(i)−{10 log₁₀(M _(PUSCH,c)(i))+P_(0,c)(j)±α_(c)(j)·PL _(c)(k)+Δ_(TF,c)(i)+f _(c)(i,l)}

In Equation 7, P_(CMAX,c)(i) may correspond to UE transmission powerconfigured for a serving cell c in PUSCH channel transmission having atransmission period i. M_(PUSCH,c)(i) may correspond to the PUSCHresource allocation bandwidth expressed in terms of the number ofresource blocks in PUSCH transmission having a transmission period i fora serving cell c. P_(0,c)(j) may be obtained by a sum of a constitutingelement P_(0_NOMINAL_PUSCH,c)(j) and P_(O_UE_PUSCH,c)(i). α_(c)(j) maybe indicated by an upper layer parameter (alpha-ue-pusch-withoutgrant).PL_(c)(k) may be a downlink pathloss estimate calculated in dB units bythe UE with respect to a serving cell c by using a reference singleresource k. Δ_(TF,c)(i) may correspond to a component for adjustingPUSCH transmission power for a serving cell c. f_(c)(i,l) corresponds toa PUSCH power control adjustment state in PUSCH transmission having atransmission period i for a serving cell c. Also, j represents aparameter set index, and l represents a PUSCH power control adjustmentstate index.

PH may be calculated with respect to current transmission and/ornon-current transmission.

Absolute TPC command mode may be supported for NR-PUSCH. And/or K_PUSCHmay also be supported. At this time, when the accumulative TPC mode issupported, K_PUSCH corresponds to the time offset (which may beinterpreted by RRC and/or a predefined table) indicating a command timeto be accumulated.

PUSCH power control in NR may support Equation 8, and Equation 8 may beused for a UE to determine power of PUSCH transmission having atransmission period i for a serving cell c.

$\begin{matrix}{{P_{{PUSCH},c}(i)} = {\min \begin{Bmatrix}{{P_{{CMAX},c}(i)},} \\{{10\; {\log_{10}\left( {M_{{PUSCH},c}(i)} \right)}} + {P_{0,c}(j)} + {{\alpha_{c}(j)} \cdot {{PL}_{c}(k)}} + {\Delta_{{TF},c}(i)} + {f_{c}\left( {i,l} \right)}}\end{Bmatrix}}} & \left\lbrack {{Equation}\mspace{14mu} 8} \right\rbrack\end{matrix}$

Regarding the parameters of Equation 8, the descriptions given forEquation 7 may be applied in the same manner.

For the pathloss measurement RS indication, k may be indicated by a beamindication for PUSCH (if present). A linkage between PUSCH beamindication and k which is the index of a DL RS resource for PLmeasurement may be preconfigured via upper layer signaling.

If PUSCH beam indication is not present, only one k value is RRCconfigured in a UE-specific manner.

The value of P₀ may be composed of a cell-specific component and aUE-specific component. At least three cell-specific component values ofP₀ may be configured.

The alpha (a) value may be 1 by default before UE specificconfiguration. Candidate values of a may be the same as in the LTE.

j may be configured by considering the following aspects:

-   -   Grant-based PUSCH, grant-free PUSCH for message (msg) 3, and        PUSCH    -   PUSCH beam indication (if present) for grant-based PUSCH    -   Logical channel of PUSCH    -   Slot sets (if supported)    -   Working assumption: for two uplinks of supplementary UL (SUL)        band combination

If N=2 (number of closed loop procedures) is configured for UE, l may beconfigured by considering the following aspects:

-   -   PUSCH beam indication (if present) for grant-based PUSCH    -   Slot sets (if supported)    -   Grant-free PUSCH and grant-based PUSCH    -   Logical channel(s) carried by PUSCH    -   Working assumption: for two uplinks of SUL band combination    -   Whether Δ_(TF) takes into account received SNR target difference        between DFT-s-OFDM and CP-OFDM or not

P_(CMAX,c) may be supported, which reports Power Headroom (PHR)corresponding to NR PUSCH only transmission. The above may be supportedat least for sub-6 GHz.

One PHR format may be supported: PH and P_(CMAX,c). The PHR report maybe restricted for short UE timeline cases (for example, virtual PHRreport).

Closed power control commands by downlink DCI for PUCCH power controland by uplink grant for PUSCH power control may be supported. And/or theabove may also be supported for SRS.

Closed power control commands by group common DCI with TPC-PUSCH-RNTI,TPC-PUCCH-RNTI, and TPC-SRS-RNTI may be supported.

Regarding NR PUCCH power control in slot i for a serving cell c,P_(CMAX,c)(i), P₀ _(PUCCH) (F), PL_(c)(k), g(i) may be supported asshown in Equation 9. In particular, Equation 9 may be used for a UE todetermine power of PUCCH transmission with a transmission period i for aprimary cell c.

$\begin{matrix}{{P_{{PUCCH},c}(i)} = {\min {\begin{Bmatrix}{{P_{{CMAX},c}(i)},} \\{P_{0\; \_ \; {PUCCH}} + {{PL}_{c}(k)} + {\log_{10}\left( {M_{{PUCCH},c}(i)} \right)} + {\Delta_{F\; \_ \; {PUCCH}}(F)} + {\Delta_{{{PUCCH}\; \_ \; {TF}},c}(i)} + {g(i)}}\end{Bmatrix}\lbrack{dBm}\rbrack}}} & \left\lbrack {{Equation}\mspace{14mu} 9} \right\rbrack\end{matrix}$

In Equation 9, P_(CMAX,c)(i) may correspond to UE transmission powerconfigured for a serving cell c in PUCCH channel transmission having atransmission period i. PL_(c)(k) may be a downlink pathloss estimatecalculated in dB units by the UE with respect to a primary cell c byusing a reference single resource k. M_(PUSCH,c)(i) may correspond tothe PUCCH resource allocation bandwidth expressed in terms of the numberof resource blocks in PUCCH transmission having a transmission period ifor a serving/primary cell c. Δ_(F_PUCCH)(F) may be provided by higherlayer parameters. Δ_(PUCCH_TF,c)(i) may correspond to a component foradjusting PUSCH transmission power for a primary cell c. g(i)corresponds to a current PUCCH power control adjustment state in PUCCHtransmission having a transmission period i for a primary cell c.

F may represent a PUCCH format index. For example, F=0 may representPUCCH format 0; F=1, PUCCH format 1; F=2, PUCCH format 2; and F=3, PUCCHformat 3.

P_(0_PUCCH) is a parameter composed of a sum of a parameterP_(0_NOMINAL_PUCCH) configured by higher layers and a parameterP_(0_UE_PUCCH) configured by higher layers.

k corresponds to the index of RS resource(s) for pathloss measurement,which are RRC configured. k values may be configured by RRC signaling.Or k may not be determined by RRC configuration.

Definition and notation of P_(CMAX,c)(i) may be changed for a regionabove 6 GHz.

In NR, full pathloss compensation for NR PUCCH power control may besupported. In Equation 9, 10*log 10(M_PUCCH,c)(i)) factor may bedeleted. Also, in Equation 9, P_(0_PUCCH) may be changed toP_(0_PUCCH)(b). Also, in Equation 9, g(i) may be changed to g(i, l).

Multiple P_(0_PUCCH)(b) may be configured by RRC signaling.

In NR, up to 2 closed-loop power control procedures (namely, l). Theclosed-loop control procedure may be configured by RRC signaling. In theclosed-loop control procedure, reset (or beam change) may be triggeredby RRC reconfiguration of P₀. In the closed-loop control procedure, onlyaccumulative TPC commands may be supported.

Also, NR may support Δ_(PUCCH_TF,c)(i) to reflect at least UCI payloadsize, UCI type (for example, SR, HARQ, CSI), different coding gains,PUCCH format, coding schemes, and other effective coding rates.Δ_(PUCCH_TF,c)(i) may or may not include M_(PUCCH,c)(i). M_(PUCCH,c)(i)may be related to the PUCCH bandwidth (BW) of slot i. Δ_(PUCCH_TF,c)(i)may take into account received SNR target difference between DFT-s-OFDMand CP-OFDM.

For PRACH/PUSCH/PUCCH/SRS on an SUL carrier associated with an NR DL/ULcarrier, the maximum pathloss including penetration loss differencebetween two UL carriers to be compensated is, for example, 76 dB. Thismaximum value is based on the assumption that the downlink carrierfrequency may be up to 70 GHz.

In NR, SRS power control may also be supported, and Equation 10 belowmay be used for determining power of SRS transmission with atransmission period i for a serving cell c.

P _(SRS,c)(i)={P _(CMAX,c)(i),P _(0_SRS,c)+10 log₁₀(M_(SRS,c))+α_(SRS,c) ·PL _(c)(k1)+h _(SRS,c)(i)}.  [Equation 10]

In Equation 10, P_(CMAX,c)(i) may correspond to UE transmission powerconfigured for a serving cell c in SRS transmission having atransmission period i. P_(0_SRS,c) and α_(SRS,c) may be provided byhigher layer parameters. M_(SRS,c) may correspond to the SRS bandwidthexpressed in terms of the number of resource blocks in SRS transmissionfor a serving cell c. PL_(c)(k1) may be a downlink pathloss estimatecalculated in dB units by the UE with respect to a serving cell c byusing a SRS resource set k1. h_(SRS,c)(i) corresponds to a power controladjustment state in SRS transmission having a transmission period i fora serving cell c.

A unified power control equation may be defined regardless of whetherSRS is intended for DL/UL CSI acquisition or beam management as shownabove (P_(SRS) _(OFFSET) _(,c) may be introduced).

In the case of h_(SRS,c)(i), at least the following may be configured byRRC for a serving cell c in which the UE is configured with PUSCH:

-   -   h_(SRS,c)(i)=f_(c)(i,l), where l=1, 2.    -   h_(SRS,c)(i)=0    -   When SRS power control is tied with PUSCH power control, an        additional closed-loop circuit for SRS power control may or may        not be supported.    -   h_(SRS,c)(i) value when SRS power control is not tied with PUSCH        power control may be defined separately.    -   h_(SRS,c) (i) may also be defined when both of the accumulative        TPC and the absolute TPC support SRS power control.    -   In the case of a serving cell c where UE is not configured for        PUSCH, the closed-loop power control process for SRS is        configured separately and is not linked to a closed-loop power        control process for PUSCH of other serving cell(s) in which the        UE is configured for PUSCH.    -   In the case of PL estimation, each SRS resource set is        associated with X1 DL reference signal(s) for PL estimation, and        X1 may be configured to be more than ‘1’. The maximum number of        PL estimates to be maintained by the UE may be limited to X2. PL        estimation associated with k1 has to be kept unchanged for each        configured SRS resource set.

It may be assumed that a UE expects the gNB to configure the same typeof time-domain behavior (namely periodic, semi-persistent, or aperiodic)for all SRS resources in an SRS resource set.

Regarding the definition of M_(SRS,c)(j), if it is assumed that M PRBsare allocated for both 15 kHz subcarrier spacing (SCS) and 120 kHz SCS,a few of alternatives may be derived as follows:

-   -   Alt. 1: M_(SRS,c)(j) may be expressed in terms of the number of        PRBs based on 15 kHz regardless of the number of PRBs allocated        for SRS transmission (for example, for 15 kHz SCS,        M_(SRS,c)(j)=M while, for 120 kHz SCS, M_(SRS,c)(j)=8M)    -   Alt. 2: M_(SRS,c)(j) may be expressed in terms of the number of        PRBs allocated for SCS transmission (for example, for 15 kHz        SCS, M_(SRS,c)(j)=M while, for 120 kHz SCS, M_(SRS,c)(j)=M)    -   Alt. 3: M_(SRS,c)(j) may be expressed in terms of the number of        PRBs based on 15 kHz SCS for the case of sub-6 GHz and in terms        of the number of PRBs based on 60 kHz SCS for above 6 GHz (for        example, for 15 kHz SCS, M_(SRS,c)(j)=M while, for 120 kHz SCS,        M_(SRS,c)(j)=2M).

In NR, since the required power for UL performance is different for eachindividual beam for a UE, differentiation of beam-specific open-loop andclosed-loop parameters between different beams for a UE may besupported.

Especially for the accumulative TPC process, however, it needs to befurther investigated about whether PC parameter separation per beamwould be superior compared with a common TPC accumulation procedureregardless of beam change or switching. The latter indicates that theTPC accumulation process is not reset even though a serving beam ischanged by a beam management procedure, considering that an alreadystabilized transmit power level is desired to be kept unchanged as muchas possible unless beam change occurs at a different TRP. As a targetservice unit requiring higher reliability such as URLLC and enhancedVehicle-to-everything (eV2X), there may be a configurable additionalpower offsets to be applied to the TPC accumulation process wheneverbeam change or switching occurs within the same TRP, by which potentialpower control mismatch due to the beam change/switching may bealleviated.

As a result, for accumulative TPC procedures, a configurable additionalpower offset to be applied to a common TPC accumulation procedure needsto be supported whenever beam change or switching occurs within the sameTRP according to a target service requiring higher reliability (forexample, URLLC and eV2X).

Regarding OLPC, proper DL RS such as an SS block (PBCH DMRS) and CSI-RSfor pathloss compensation needs to be defined at least for UEssupporting beam correspondence. This behavior may be expressed in termsof the following parameters.

For OLPC, at least one of P_(cmax,c), M_(PUSCH,c)(i), P_(0,c)(j),α_(c)(j), and PL_(c)(k) parameters as described in detail with referenceto Equation 7 may be supported for NR PUSCH power control for a servingcell c, where i may correspond to the slot number/index, j the parameterset number/index, and k DL RS number/index. In addition, support forother parameters (for example, Δ_(TF,c)) is not precluded. Based on theparameters, PUSCH transmission power may be determined/calculated byEquation 11 below.

$\begin{matrix}{{P_{{PUSCH},c}(i)} = {\min \begin{Bmatrix}{P_{{CMAX},c},} \\{{10\; {\log_{10}\left( {M_{{PUSCH},c}(i)} \right)}} + {P_{0,c}(j)} + {{\alpha_{c}(j)} \cdot {{PL}_{c}(k)}} + {f_{c}\left( {i,j} \right)}}\end{Bmatrix}}} & \left\lbrack {{Equation}\mspace{14mu} 11} \right\rbrack\end{matrix}$

A characteristic point in Equation 11 is that k which indicates aspecific DL RS index for PL calculation may be variable/different foreach j which is an (OL)PC parameter set index (namely for each parameterset). This indicates that a basic PC equation is determined/calculatedbased on a specific/fixed (OL)PC parameter set j and thereby, indicateswhich DL RS(s) index k is applied/linked may be varied. In other words,it indicates that a variable DL RS (index k) may be applied to aspecific/fixed parameter set (index j).

As described above, when the equation 11 is applied to a specific (OL)PCparameter set j, it is necessary to propose a method for determining aDL RS(s) index k associated with the parameter set. Therefore, in whatfollows, various methods for determining k are proposed, and at leastone of the following methods may be applied. Methods for determining kmay be divided into implicit indication methods, explicit indicationmethods and/or methods mixing/combining the aforementioned methods:

a) Implicit Indication Method

A UE may be defined/configured/indicated to directly apply the index k′of specific DL RS(s) (for example, ((spatial)-QCLed) CSI-RS resource(s)(expressed in terms of CRI) and/or SS block(s))configured/linked/applied (by a PDCCH beam indication) to a specific (orserving) control (channel) resource set (CORESET) as a DL RS(s) index k(namely k=k′). The implicit indication method may beapplied/defined/configured as a kind of “default (and/or fallback)behavior” performed before other indication method (for example,explicit indication method) is applied. In other words, before otherexplicit indication is received, the UE may be defined/configured toapply the index k′ of DL RS(s) (which, for example, includes SS block(s)used for initial access (for example, discovered/attached during a RACHprocedure)) associated/linked (for the purpose of spatial QCL) to aspecific CORESET (in particular, serving-CORESET (CORESET for which aserving PDCCH is configured) and/or primary CORESET) configure/indicatedfor the UE itself as the k (namely the DL RS index k used for PUSCHtransmission power calculation). At this time, although the UE mayfollow a separate indication (for example, explicit indication method)proposed in the present specification, if it is the case that ambiguitymay be caused about which operation the UE has to follow while thecorresponding indication operation is reconfigured (by RRC and/or MACCE), the “fallback operation” may indicate an alternative/defaultoperation which may be applied for the aforementioned case. And/or the“fallback operation” may indicate an alternative/default operation whichmay be applied for a special situation in which ambiguity may be causedduring a process where the UE enters discontinuous reception (DRX)and/or idle mode from RRC-connected state and transitions back to activemode.

If one or more DL RS(s) are configured (for the specific (OL)PCparameter set j), which DL RS (for example, k-th DL RS) is to be appliedfor PL calculation among the plurality of DL RSs may bedefined/configured by UE implementation (namely an independent operationof the UE itself). In other words, if it is the case that the eNB hasconfigured one or more DL RS(s) for the UE from the start, the UE mayselect/consider only appropriate, specific RS(s) (which shows/has thebest measurement value) within the configured DL RS(s) and apply theselected/considered RS(s) for PL calculation.

b) Explicit Indication Method

A UE may be configured/indicated with information related to DL RS(s)index k (or a set of ks) which may be applicable (or which has to beapplied) for each specific (OL) PC parameter set j. The explicitindication/configuration may be delivered to the UE through RRC and/orMAC CE signaling. For example, the eNB configures the UE with kset-related DL RS(s) set information through RRC signaling; then, fromthe information, the eNB may transmit, to the UE through MAC CEsignaling, an activation indication (or deactivation of other RS(s)which should not be applied) for a specific DL RS(s) (index) which hasto actually/currently be applied. And/or through MAC CE signaling, theeNB may configure/indicate the UE with an operation forupdating/replacing preconfigured, k set-related DL RS(s) set informationwith new information.

Among the proposed operations/methods, for at least one of them, whetherthe corresponding operation/method itself is activated (or may beactivated) may be configured/indicated by a higher layer indication (forexample, by RRC and/or MAC CE signaling).

It is apparent that the proposed PUSCH PC methods, described withreference to PUSCH above, may be applied to the PUCCH PC methods in thesame/similar manner (in other words, in the methods above, PUSCH may bereplaced with PUCCH). For example, configurations for the DL RS(s) (withindex k) for PUCCH PL calculation may be provided from a higher layer byRRC signaling/parameters as shown below:

-   -   ‘num-pucch-pathlossReference-rs’: this parameter indicates the        number of DL RS configurations for measuring pathloss. For each        configuration, an individual pathloss estimate is maintained by        the UE and is used for PUCCH power control. The number of RS        configurations may be N, where N is 1, 2, 3, or 4 (which        indicates 1 to 4 pucch-pathlossReference-config).    -   ‘pucch-pathlossReference-rs-config’: this parameter indicates        configuration of RS (for example, CSI-RS configuration or SS        block) used for PUCCH pathloss estimation. The number of RS        configurations may be N, where N is 1, 2, 3, or 4 (which        indicates pucch-pathlossReference-rs ranging from 1 to the        number indicated by num-pucch-pathlossReference-rs).

At this time, for example, when all of the DL RSs with an index N=1, 2,3, 4 in the upper layer (for example, CSI-RS configuration or SS block)are explicitly configured/provided to the UE, it is necessary toexplicitly specify which of the N DL RSs to apply to which PUCCHtransmission. Therefore, a UE/eNB operation according to at least one ofthe following options for specifying explicitly which one to apply towhich transmission:

a) Option 1

First of all, the implicit indication method proposed above may bedefined/configured. For example, according to option 1, in the case ofPUCCH transmission triggered by DCI detection (for example,event-driven) from the DL control channel transmitted through a specificCORESET such as the PUCCH intended for ACK/NACK transmission (namely, inthe case where PUCCH transmission is triggered by the DL control channeltransmitted through the CORESET), the UE may apply the DL RSlinked/associated/related to the DL control channel which has triggeredthe corresponding PUCCH transmission (for example, a (spatially) QCLedDL RS to a PDCCH DMRS) to the PL calculation. In this case, even if theDL RS associated/linked/related to the DL control channel (for example,the (spatially) QCLed DL RS to the PDCCH DMRS) does not belong to a listof N upper-layer configured/signaled DL RSs, the UE may still apply/usethe DL RS associated/linked/related to the DL control channel as a DL RSof PL calculation for the PUCCH PC. And/or only when the DL RS (forexample, (spatially) QCLed DL RS) coincides with a specific DL RSbelonging to the list including N upper-layer configured/signaled DL RSs(namely, only when the DL RS belongs to the list), a condition forapplication/use, which indicates the DL RS to be applied/used as a DL RSof PL calculation for the PUCCH PC, may be specified/configured.

b) Option 2

Among N configured DL RSs, the n-th (n=1, 2, . . . , N) RS islinked/applied to a specific PUCCH resource configuration (for example,through upper layer signaling, dynamic signaling and/or implicitsignaling). In other words, a configuration such that a specific DL RS(or a DL RS in a specific order) among N DL RSs is associated/tied witha specific PUCCH resource configuration (namely each DL RS is configuredto be associated with/to correspond to/to be mapped to a specific PUCCHresource configuration) may be provided to a UE.

As one embodiment, which PUCCH resource configuration is provided to theUE may be configured/signaled separately by the upper layer. At thistime, each PUCCH resource configuration, for example, may be one PUCCH(resource) configuration unit accompanied by a specific configurationparameter such as a specific PUCCH format/type/resource. At this time,to allow the n-th DL RS to be used/applied for PL calculation for thek-th PUCCH resource configuration, the linkage between the two may beconfigured/indicated explicitly and/or implicitly. At this time, n mayrepresent the index/order of a DL RS, and k may represent theindex/order of a PUCCH resource configuration.

As an example where the linkage is implicitly configured/indicated, asituation where n=1 or 2 (namely a total of two DL RSs), and k=1, 2, or3 (namely a total of three PUCCH resource configurations) may beassumed. In this case, two DL RSs may be mapped/linked sequentially tothree PUCCH resource configurations as follows.

-   -   For PUCCH resource configuration k=1, RS for n=1 for PL        calculation is implicitly associated.    -   For PUCCH resource configuration k=2, RS for n=2 for PL        calculation is implicitly associated.    -   For PUCCH resource configuration k=3, RS for n=1 for PL        calculation is implicitly associated.

In other words, like a method where n is sequentially and implicitlylinked/associated/mapped to each PUCCH resource configuration one by one(for example, in the ascending or descending order), and when one-to-onelinkage/association/mapping of PUCCH resources is completed for all n, nis reset to 1 and is again sequentially and implicitlylinked/associated/mapped to the remaining (k−n) PUCCH resourceconfigurations one by one, a pre-defined/pre-configured/pre-determinedrule which circulates implicit linkage/association/mapping of n to k maybe proposed (at this time, k may also be sequentially and implicitlylinked/associated/mapped to n (for example, in the ascending ordescending order). In this case, N-to-1 relationship may be establishedbetween k and n. According to the rule, the UE may associate a DL RSwith a PUCCH resource configuration without ambiguity and apply the DLRS associated with the PUCCH resource configuration to PL calculation.

In another example, if n=1 or 2 (namely, a total of two DL RSs) and k=1,2, 3, 4, or 5 (namely, a total of 5 PUCCH resource configurations), kand n may be linked/associated/mapped to each other without ambiguity asfollow.

-   -   For PUCCH resource configuration with k=1, RS for n=1 for PL        calculation is implicitly associated.    -   For PUCCH resource configuration with k=2, RS for n=2 for PL        calculation is implicitly associated.    -   For PUCCH resource configuration with k=3, RS for n=1 for PL        calculation is implicitly associated.    -   For PUCCH resource configuration with k=4, RS for n=2 for PL        calculation is implicitly associated.    -   For PUCCH resource configuration with k=5, RS for n=1 for PL        calculation is implicitly associated.

Embodiments modified in a particular manner according to an objectsimilar to the above (for example, an object to link a DL RS for PLcalculation to a PUCCH resource configuration through implicitlinkage/association/mapping without ambiguity) also belong to thetechnical scope of the present invention.

And/or it is also possible to apply a method which combines/links theoption 1 and 2 by configuring a priority condition for the two options.For example, the method may be configured/defined/indicated so that a UEapplies the option 1 first (in other words, for a specific PUCCHresource configuration, a DL RS linked/associated/related to a DLcontrol channel which has triggered PUCCH transmission is applied to PLcalculation regardless of a list including N configured DL RSs or onlywhen the DL RS coincides with at least one of N configured DL RSsbelonging to the list), and/or for a specific PUCCH resourceconfiguration to which the option 1 is not applied (for example, whenthe condition for applying the option 1 is not satisfied and/or when thecorresponding situation is not relevant to applying the option 1 (forexample, PUCCH transmission is not triggered by a specific DL controlchannel (for example, CSI reporting PUCCH and PUCCH for beam managementand/or beam failure recovery)), the option 2 is applied. In other words,the UE may apply the option 1 by default, but when the condition for theoption 1 is not satisfied (or when the condition for the option 2 issatisfied), the option 2 may be applied exceptionally.

As an example of the description above, if it is assumed that n=1 or 2(namely, a total of two DL RSs), and k=1, 2, 3, 4, or 5 (namely, a totalof 5 PUCCH resource configurations), n and k may belinked/associated/mapped to each other as follows.

-   -   For PUCCH resource configuration with k=1, RS following the        option 1 is applied for the PL calculation.    -   For PUCCH resource configuration with k=2, RS for n=1 for PL        calculation is implicitly associated.    -   For PUCCH resource configuration with k=3, RS following the        option 1 is applied for the PL calculation.    -   For PUCCH resource configuration with k=4, RS for n=2 for PL        calculation is implicitly associated.    -   For PUCCH resource configuration with k=5, RS for n=1 for PL        calculation is implicitly associated.

In other words, according to the embodiment above, each PUCCH resourceconfiguration may be linked/associated/mapped to a specific DL RSindependently (according to the option 1 and/or option 2).

According to the method described above, a UE operation which determinesa DL RS to be applied for PL calculation may bedefined/configured/indicated.

The core components of the proposed methods may also be applied/extendedto other UL transmission (for example, PUSCH transmission) in thesame/similar way (in other words, in the embodiments above, PUCCH may bereplaced with PUSCH). For example, like the PUCCH transmission above, anenvironment/system configured/distinguished by a specific PUSCH (or SRS)resource configuration may be linked/designated to a specific DL RS foreach PUSCH resource configuration as in the embodiment/option above.

In the case of closed-loop power control (CLPC), an independentaccumulative TPC command may be supported for each open-loop parameterset (namely f_(C)(i,j)). Here, f_(C)(i,j) may reset triggering (forexample, reconfiguration of a parameter set and/or explicit signaling).

Considering UL-CoMP operations, different DL RSs for pathlosscompensation may be configured for each SRS resource for UL CSIacquisition. For UEs without beam correspondence, the pathlosscompensation may be performed by pre-defined/configured function or rulebased on a default type of DL RSs such as a set of SS blocks (PBCH DMRS)or configured CSI-RSs. In other words, information such as “a set of SSblocks (PBCH DMRS) or configured CSI-RSs” may be configured separatelyfor a UE (for example, by RRC, MAC and/or DCI), the UE may perform apathloss compensation operation according to/based on the configuration.And/or even if the UE is not configured separately, a DL RS for pathlosscompensation may be limited to a specific (for example, default orlowest (or highest)-indexed (according to sorting by an average powerlevel (for example, RSRP) and/or (previously/most recently) reporting atleast one with the best power level according to the sorting)) “set ofSS blocks (PBCH DMRS) or configured CSI-RSs” for a serving cell. And/oralong with the operation, a specific calculation function such as maxfunction or some weighted averaging function may be defined/configured.

As a result, for OLPC, proper DL RS for pathloss compensation has to bedefined or configured for each SRS resource, and apre-defined/configured function for the pathloss compensation has to bedetermined for UEs without beam correspondence.

Considering codebook-based transmission for UL, SRI in UL grant mayindicate multiple selection of SRS resources capable of supportingmulti-panel joint transmission in UL. Furthermore, each paneltransmission associated with each indicated SRS resource may targetdifferent UL reception point in the context of UL-CoMP. To properlysupport this, NR network needs to be able to at least calculate accurateMCS for each different layer group corresponding to different SRSresource, by using a power control process separated for each SRSresource.

Generally, multiple ULPC processes for a UE need to be supported, andeach ULPC process may be associated with at least one SRS resourceconfigured to the UE. For example, while configured SRS resources ID #1and #2 may be associated to the same ULPC process A, another configuredSRS resource ID #3 may be associated to a different ULPC process B. ULPCprocesses A and B may target different reception points, and the SRSresources #1 and #2 which follow the same ULPC process A may bedynamically selected by the SRI indication in UL grant. When SRSresources #1 and #3 are jointly indicated by the SRI field in UL grant,for example, it may be interpreted as layer-group-separated ULmulti-panel transmission and UL-CoMP joint reception operations at thegNB side.

In other words, independent power control may be employed for eachindicated SRS resource, and/or the number of ranks/layers may beindicated/provided separately (in the same UL grant) for each indicatedSRS resource, and/or (separate) TPMI information according to the numberof ranks/layers may be indicated/provided (in the same UL grant) foreach indicated SRS resource.

As a result, to properly support multi-panel UL transmission and UL-CoMPoperations, multiple ULPC processes for a UE has to be supported, andeach ULPC process may be associated with at least one SRS resourceconfigured to the UE.

FIG. 9 is a flow diagram illustrating a method for UL power control of aUE according to one embodiment of the present invention. The embodimentsdescribed above may be applied in the same/similar manner with respectto the flow diagram, and repeated descriptions thereof will be omitted.

First, the UE may receive a DL RS (S910). At this time, the DL RS maycorrespond to a CSI-RS and/or an SS block.

Next, the UE may measure DL pathloss by using the received DL RS (S920).

Next, the UE may determine transmission power of an UL channel by usingmeasured pathloss (S930). The UL channel may correspond to the PUCCH orthe PUSCH. The DL RS used for/as a basis for determining transmissionpower of the UL channel may be determined according to variousembodiments based on the configuration information indicated by an eNB,where the configuration information may be indicated through RRCsignaling (and/or MAC CE signaling).

As an embodiment, the configuration information may include/indicate thenumber of DL RSs for determining UL channel transmission power and/orindex of a DL RS, and in this case, the UE may determine the DL RSindicated by the corresponding configuration information as the DL RSfor obtaining/calculating/determining transmission power of the ULchannel.

As another embodiment, if a specific DL RS indicated throughconfiguration information is determined as the DL RS for determining ULchannel pathloss, the specific DL RS may be updated in real time throughMAC CE signaling. In other words, it may be interpreted that a DL RS isconfigured for a long-term basis through RRC signaling, and the DL RS isupdated through MAC CE in a short-term basis.

As other embodiment, if a plurality of DL RSs are indicated throughconfiguration information, a specific DL RS indicated through MAC CEsignaling among the candidate DL RSs may be determined as a DL RS fordetermining UL channel transmission power.

As other embodiment, if there are a plurality of UL channels to betransmitted by the UE (in other words, there are multiple UL channels),a DL RS for determining UL channel transmission power may be determinedindependently for each UL channel resource configuration mapped to eachof the plurality of UL channels. If at least one candidate DL RS isindicated through configuration information, a specific candidate DL RSassociated with each UL channel resource configuration may be determinedas a DL RS for determining UL channel transmission power. At this time,each UL channel resource configuration may be mutually associated withat least one candidate DL RS based on an index of each UL channelresource configuration, and an index of at least one candidate DL RS.For example, the indexes of a candidate DL RSs may be associated in theascending order (or descending order) in a cyclic manner with theindexes of a plurality of UL channel resource configurations in theascending order (or descending order), detailed descriptions of whichare the same as in the embodiment above.

As other embodiment, a specific DL RS associated with the CORESETconfigured for the UE through configuration information may bedetermined as a DL RS for determining UL channel transmission power. Inparticular, if transmission of an UL channel is triggered by the DLchannel transmitted through the CORESET, the specific DL RS maycorrespond to a CSI-RS and/or an SS block Quasi-co-Located (QCLed) withthe DL channel transmitted through the CORESET. At this time, if atleast one candidate DL RS is indicated through configurationinformation, the specific DL RS may be determined as a DL RS fordetermining UL channel transmission power only when the specific DL RSis included in the at least one candidate DL RS.

Lastly, the UE may transmit the UL channel (with the determinedtransmission power) (S940).

Meanwhile, although not shown in the flow diagram, if the UE receives abeam change (and/or switching) indication for the eNB, transmissionpower of the determined UL channel may be boosted as much as the amountof preconfigured power. In particular, this operation may be supportedfor providing a service requiring high reliability such as V2X, URLLC,and eMBB.

The Device to which the Present Invention May be Applied in General

FIG. 10 illustrates a block diagram of a wireless communication deviceaccording to one embodiment of the present invention.

Referring to FIG. 10, a wireless communication system comprises an eNB1010 and a plurality of UEs 1020 located within the range of the eNB1010.

The eNB 1010 comprises a processor 1011, memory 1012, and RF (RadioFrequency) unit 1013. The processor 1011 implements the functions,processes and/or methods described above. Layers of a wireless interfaceprotocol may be implemented by the processor 1011. The memory 1012,being connected to the processor 1011, stores various kinds ofinformation to operate the processor 1011. The RF unit 1013, beingconnected to the processor 1011, transmits and/or receives a radiosignal.

The UE 1020 comprises a processor 1021, memory 1022, and RF unit 1023.The processor 1021 implements the functions, processes and/or methodsdescribed above. Layers of a wireless interface protocol may beimplemented by the processor 1021. The memory 1022, being connected tothe processor 1021, stores various kinds of information to operate theprocessor 1021. The RF unit 1023, being connected to the processor 1021,transmits and/or receives a radio signal.

The memory 1012, 1022 may be installed inside or outside the processor1011, 1021 and may be connected to the processor 1011, 1021 via variouswell-known means. Also, the eNB 1010 and/or the UE 1020 may be equippedwith a single antenna or multiple antennas.

The embodiments described above are combinations of constitutingelements and features of the present invention in a predetermined form.Each individual element or feature has to be considered as optionalexcept where otherwise explicitly indicated. Each individual element orfeature may be implemented solely without being combined with otherelements or features. Also, it is also possible to construct theembodiments of the present invention by combining a portion of theelements and/or features. A portion of a structure or feature of anembodiment may be included in another embodiment or may be replaced withthe corresponding structure of feature of another embodiment. It shouldbe clearly understood that the claims which are not explicitly citedwithin the technical scope of the present invention may be combined toform an embodiment or may be included in a new claim by an amendmentafter application.

Meanwhile, the term ‘A and/or B’ in this document may be interpreted asindicating at least one of A and/or B.

An embodiment of the present invention may be implemented by variousmeans, for example, hardware, firmware, software or a combination ofthem. In the case of implementations by hardware, an embodiment of thepresent invention may be implemented using one or moreApplication-Specific Integrated Circuits (ASICs), Digital SignalProcessors (DSPs), Digital Signal Processing Devices (DSPDs),Programmable Logic Devices (PLDs), Field Programmable Gate Arrays(FPGAs), processors, controllers, microcontrollers and/ormicroprocessors.

In the case of implementations by firmware or software, an embodiment ofthe present invention may be implemented in the form of a module,procedure, or function for performing the aforementioned functions oroperations. Software code may be stored in the memory and driven by theprocessor. The memory may be placed inside or outside the processor, andmay exchange data with the processor through a variety of known means.

It is evident to those skilled in the art that the present invention maybe materialized in other specific forms without departing from theessential characteristics of the present invention. Accordingly, thedetailed description should not be construed as being limitative fromall aspects, but should be construed as being illustrative. The scope ofthe present invention should be determined by reasonable analysis of theattached claims, and all changes within the equivalent range of thepresent invention are included in the scope of the present invention.

INDUSTRIAL APPLICABILITY

The present invention applied to a 3GPP LTE/LTE-A/NR system is primarilydescribed as an example, but may be applied to various wirelesscommunication systems in addition to the 3GPP LTE/LTE-A/NR system.

1. A method for uplink (UL) power control of a User Equipment (UE) in awireless communication system, comprising: receiving a Downlink (DL)Reference Signal (RS); measuring DL path-loss by using the DL RS;determining transmission power for an UL channel by using the measuredpath-loss; and transmitting the UL channel, wherein the DL RS used fordetermining the transmission power for the UL channel is determinedbased on configuration information indicated by a base station.
 2. Themethod of claim 1, wherein the UL channel corresponds to a PhysicalUplink Control Channel (PUCCH) or a Physical Uplink Shared Channel(PUSCH).
 3. The method of claim 2, wherein the DL RS corresponds to aChannel State Information (CSI)-RS and/or a SynchronizationSignal/Sequence (SS) block.
 4. The method of claim 3, wherein theconfiguration information is indicated through Radio Resource Control(RRC) signaling.
 5. The method of claim 4, wherein the configurationinformation includes the number of the DL RS and/or index of the DL RS.6. The method of claim 4, wherein, when the DL RS is determined as aspecific DL RS indicated through the configuration information, thespecific DL RS is updated through Medium Access Control (MAC) ControlElement (CE) signaling.
 7. The method of claim 4, wherein, when aplurality of candidate DL RSs are indicated through the configurationinformation, the DL RS is determined as a specific DL RS indicatedthrough Medium Access Control (MAC) Control Element (CE) signaling amongthe candidate DL RSs.
 8. The method of claim 4, wherein, when thereexists a plurality of the UL channels to be transmitted, the DL RS isdetermined independently for each UL channel resource configurationmapped to each of the plurality of the UL channels.
 9. The method ofclaim 8, wherein, when at least one candidate DS RS is indicated throughthe configuration information, the DL RS is determined as a specificcandidate DL RS associated with each of the UL channel resourceconfigurations.
 10. The method of claim 9, wherein each of the ULchannel resource configurations is mutually associated with the at leastone candidate DL RS based on an index of each of the UL channel resourceconfigurations and an index of the at least one candidate DL RS.
 11. Themethod of claim 4, wherein the DL RS is determined as a specific DL RSassociated with a Control Resource SET (CORESET) set for the UE throughthe configuration information.
 12. The method of claim 11, wherein, whentransmission of the UL channel is triggered by a DL channel transmittedthrough the CORESET, the specific DL RS corresponds to the CSI-RS and/orthe SS block Quasi-co-Located (QCLed) with a DL channel transmittedthrough the CORESET.
 13. The method of claim 11, wherein, when at leastone candidate DL RS is indicated through the configuration information,the specific DL RS is determined as the DL RS only when the specific DLRS is included in the at least one candidate DL RS.
 14. The method ofclaim 4, further comprising, when a beam change indication for the basestation is received, increasing transmission power of the determined ULchannel as much as the amount of preconfigured power.
 15. A UserEquipment (UE) performing Uplink (UL) power control in a wirelesscommunication system, comprising: a Radio Frequency (RF) unit fortransmitting and receiving a radio signal; and a processor forcontrolling the RF unit, wherein the processor is configured to: receivea Downlink (DL) Reference Signal (RS); measure DL path-loss by using theDL RS; determine transmission power of a UL channel by using themeasured path-loss; and transmit the UL channel, wherein the DL RS usedfor determining the transmission power for the UL channel is determinedbased on configuration information indicated by a base station.